So this takes place right around Season 2, Episode 7, "Dance Dance Infiltration" but it's an alternate take on what could have happened, assuming there was no Nefarious Plot from Cinder. This is how I imagine Ruby and Weiss first started their relationship.
The incident happened so fast that Ruby had barely a moment to process it. It all started when her feelings towards the matter had become a struggle for the past few weeks, turning and boiling inside of her stomach like hot oil. She was losing sleep, she couldn't eat and training and even missions were being awkward. She didn't want to admit it at first, but it was becoming more and more apparent and she couldn't lie to herself anymore - she was in love with Weiss Schnee.
Naturally, there was only person she could talk to and that was Yang. So one day, after classes had let out and Weiss and Blake were occupied somewhere else on campus, Ruby broke down and told Yang everything. Surprised at first by the confession, Yang turned out to be a good listener and let Ruby rant and get everything off her chest.
"...and I just don't know what this means, Yang! Weiss can't stand me and I can't crush on her! Am I...-g-gay? A lesbian? I just...urgh! I don't know, everything is so confusing!" she said, plopping down on the side of Blake's bed. Yang smiled warmly and rubbed Ruby's hair.
"Sis, just because you have a crush on a girl doesn't mean you're gay or straight or anything like that. Love is love. Just like who you like and don't worry about the labels." said Yang. Ruby sighed.
"I know, but it's just...I always figured eventually I would get a boyfriend someday. But now I'm sitting here daydreaming about having Weiss, Weiss Schnee, as a girlfriend! She totally has the hots for Neptune, sis! She's about as into girls as Jaune is into hand-to-hand combat." Yang snorted with laughter at this, before giving her sister and team leader a massive side hug.
"You know what I do when I'm faced with a problem?"
"You get really mad and then punch it?"
"Ha, guilty as charged!" Yang said with a chuckle. "but in all seriousness, I approach the problem head-on. You just gotta rip that band-aid off and go for broke."
"But...I don't have a band-aid?" Ruby said in confusion.
"No, it's a metaphor. Look, Rubes - you know I'm not the one to BS you, right? So what you have to do is simple - ask Weiss to the Beacon Dance next week."
"Are you kidding?!" Ruby said, standing up and flailing her arms. "Ask Weiss to the Beacon Dance?! Why don't I give Cardin a wedgie while I'm at it?! Maybe call Velvet a nude model in front Coco?! Cause these are all great decisions!"
Now it was Yang's turn to stand up, firmly placing both her hands on Ruby's shoulders and squeezing them tightly.
"You are over thinking this! Just ask her! If she says no, she says no. You were planning on going by yourself, right? So the worst that can happen is that your plans stay the same!" Yang said. Ruby exhaled with defeat, her shoulders slumping and her posture going slack.
"I guess it wouldn't hurt. I'll ask her tomorrow on the way to breakfast."
"That'a girl!" Yang cheered, pumping her fist in the air. "I got a good feeling about this one, sis."
Ruby barely slept that night. Tossing and turning in her bunk, she kept glancing at her Scroll to check the time, dreading the 6:30 AM alarm forcing her to be up, showered and dressed in uniform to walk to the cafeteria for breakfast. When she finally drifted off to sleep, her alarm buzzed soon after and cut through the pre-dawn air like Crescent Rose slicing through warm Grimm flesh. To the rest of the girls, it had to have felt like an everyday morning, but to Ruby, she felt like she was on death row, waiting for the warden to call her to take the long trip down the hallway and never return.
After everyone was dressed and Weiss made sure her hair and makeup were to her levels of satisfaction, Team RWBY made their way down the hall and out the dorm to the main courtyard and then to the cafeteria. Usually, all four of them would be discussing whatever the topic du jour was, be it an upcoming test, a recent Grimm battle, or heckling Weiss about Jaune's frequent attempts to woo her. But this time Yang was in full Big Sister mode and pulled Blake back a bit to keep her separated from the group, leaving just Weiss and Ruby several feet ahead of them.
"So, uh, nice weather, huh?" Ruby said with a hoarse whimper. Weiss merely shrugged.
"It's acceptable, I suppose."
"Heh, yeah. Totally acceptable. I was thinking the same thing." Ruby stammered. Glancing back at Yang for support, her older sister was pointing up to encourage Ruby to keep the conversation going, mouthing silent words of support. Ruby let out a soft moan of irritation and cleared her throat. "So Weiss, next Friday is the Beacon Dance. Are you, uh, going?"
"More than likely," Weiss said off-handedly. She wasn't even bothering to make eye contact with Ruby but was glancing over her notes from the night before for the big test tomorrow. "Are you?"
"Who me? Heh, you know...uh, sooooo many boys are just beating down my door to ask me. Can't keep track of them!" Ruby quavered with a nervous smile. Weiss merely cocked a confused eyebrow, before returning to her notes. "But that's not to say I couldn't get a date later, you know! I mean, I like to keep my options open."
"Well, good for you, I suppose," Weiss replied, only the slightest hint of emotion in her voice. "I had intended to have a partner for this dance, but it looks like I'm going solo."
"REALLY? I mean, really? That's, you know, too bad." Ruby said, sputtering her words in a nervous tumble out of her mouth.
"Is there some point to any of this conversation, Ruby? I really need to get back to studying. If I can't bring my A- up to an A+, I'm going to hear it from my sister and I really don't want to have to answer that Scroll call."
"Oh, uh, no, everything is fine. Just peachy. Juussssst peachy. All peaches over here. I'm practically the Queen of Peaches. Yep. Soooo many peaches." Ruby rambled. Weiss just shook her head in annoyance and walked a bit faster to get to the cafeteria before the rest of her team. Yang waited till Weiss had a good bit of distance between them before speeding up to walk side by side with her sister.
"Just what was that?! You didn't ask her out at all!" she protested, her violet eyes showing the slightest bit of turning red.
"I'm sorry!" Ruby whined, burying her head in her hands. "I chickened out, I couldn't do it." Blake, who had been a silent witness to all of this, looked confused.
"Wait, what am I missing? What's going on here?" she asked, her cat ears twitching underneath her bow.
"Rubes has a crush on Weiss and wanted to ask her out to the dance but she wussed out in the end," Yang said with an annoyed shrug. Ruby's face blushed as red as a thousand rose petals.
"YANG! That's not supposed to be public knowledge!" she pouted, stomping her foot in anger.
"Hey, she's our teammate, sis! She's saved our rear ends more times than I can count, so if anyone should know, it's her." Yang said. Blake blushed slightly at the unexpected compliment.
"I appreciate the sentiment, but if you really do have feelings for Weiss, you should ask her out. You have everything to gain and nothing to lose." Blake appealed. Ruby grunted in irritation.
"I have everything to lose, Blake!" Ruby fumed, her silver eyes hard. "Weiss already can't stand me and me confessing that I have a crush on her is going to smash whatever good vibes there are between us! Can you imagine having to be a teammate with someone who thinks about giving you smooches and cuddles all day long?!"
"No, I can't," Blake mused, giving Yang a coy, sarcastic smile. Yang's cheeks flushed crimson and she briefly broke eye contact with the golden-eyed Faunas.
"Point is, I'm not telling her anything. I'm just going to go to this stupid dance in my stupid lady stilts and drink a ton of fruit punch and then go home and play video games all night and then we never ever talk about this again. Good? Good. Now if you excuse me, it's omelet day and I do not want to miss out!" Ruby huffed, pushing open the large wooden doors to the cafeteria and letting them slam behind her.
"So...that was a thing." Yang lamented.
"Honestly? I think they would make a cute couple." Blake observed, opening the cafeteria doors.
The actual dance had been as much fun as watching paint dry for Ruby. She had spent most of it hovering by the punch bowl, watching everyone else dance and have fun. True to her word, Weiss was there, but the platinum-haired heiress spent most of the night making sure the decorations were in order and all the chairs were pushed in. Ruby's heart ached to see Weiss alone like that and she wanted nothing more than to ask her to a dance, even if it was just a random silly song and not even a slow romantic ballad. The RWBY Team Leader sighed dejectedly and took another sip of the syrupy sugary fruit punch.
"Penny for your thoughts?"
"Huh?"
Startled, Ruby turned around to see Pyrrha standing beside her, looking amazingly elegant and beautiful in a floor-length blood-red dress. It complemented her emerald eyes perfectly and made them shine like two gemstones.
"Sorry if I snuck up on you," Pyrrha said, slightly embarrassed. "But you seemed to be rather alone up here so I thought I might come and keep you company?"
"Oh, yeah, I don't mind. I'm afraid I'm not much company anyway." Ruby muttered, refilling her cup full of punch for the umpteenth time.
"We shall see about that. I must admit, your dress looks very lovely on you." Pyrrha said with a warm smile. Ruby blushed a bit. Yang had picked this outfit out for her, as she had no idea what to possibly wear. Yang had picked out a short, red, sleeveless dress with a thick black sash around the waist and black trim along the bottom along with black pumps and black stockings.
"Heh, thanks. I don't know much about fancy lady clothes, so Yang picked this out for me." Ruby admitted.
"Well, she did a wonderful job. I'm honestly surprised there isn't a handsome gentleman at your arm." Pyrrha said with genuine warmth in her voice. But Ruby just gave out a bitter, sharp, sarcastic chuckle.
"Who, me? Ha. No, no boys asked me, at all. But..." Ruby sighed, letting her shoulders slump. "Pyrrha, can I ask you a question?"
"Of course! I realize we do not have much interaction outside of the occasional mission, but I do consider you a friend. You can tell me anything."
"What if...what if there was someone you were madly in love with, right? And you have these...feelings...for them and you want to tell them, tell them so bad! But you're afraid of rejection and you don't want to ruin what you already have with them. What...I dunno, what would you do?" Ruby said, before realizing who she was talking to. Pyrrha's face burned a deep shade of scarlet as she struggled to find an appropriate response.
"Well, um..I-I'm sure your situation is, pro-probably one that is, um, causing you distress...but, personally, I-I feel that-" she stuttered. Ruby immediately felt guilty.
"Oh, no! I'm sorry! I forgot that you and well, Jaune and-"
"No, no, it's fine," Pyrrha said, having regained some of her cool. "But to answer your question, speaking from experience, I would say it's best to confront the issue and address your feelings for this person. Otherwise, your moment will pass and by then it may be too late to say anything." Ruby frowned as this was basically the same thing Yang and Blake had told her and she was desperately hoping someone would tell her something different. "Also, if I may be so bold, who is this lucky gentleman that you have feelings for?"
"Well, heh, that's the thing. It's not so much a gentleman as it is a gentlewoman." Ruby laughed nervously, rubbing the back of her head. Pyrrha's eyes went wide with shock.
"Oh, I had no idea." she finally said.
"Yeah, and it's bad because she has no idea, right? No clue! And if I told her, I think she would flip! Especially, well...I can trust you, right? It's Weiss. I have a crush on Weiss and I don't know what to do!"
"Ruby, I-"
"And I know I get on her nerves and I know I can be irritating to her, but...dang it all, she's just so pretty! When she walks into the room, my heart just freezes up and I can't breathe."
"I understand, but I really feel that-"
"And everyone keeps telling me that I should just confront it head on, ask her out on a date and be done with it! But this is Weiss Schnee! What am I supposed to do? 'Oh hi, Weiss! Great job killing that Grimm last week. Say, are you busy next weekend? Maybe we can have cute lesbian smooches?!"
"...is that how you really feel about me?" Weiss said softly from behind Ruby. The color drained from Ruby's face, her entire body froze.
"I had been trying to tell you, she was walking right behind you.." Pyrrha said bashfully. Ruby's throat tightened, her tongue stopped working and her vocal chords shut down. Every cell in her body had completely solidified like she was made of concrete or steel.
"Is there someplace we can talk about this privately?" Weiss asked, her voice calm. Ruby, however, was not and after a few moments of awkward silence, she disappeared in a poof of rose petals, leaving behind two perfectly good black pumps.
"Is she going to be okay?" Pyrrha asked, her voice fraught with worry.
"I'm not sure," Weiss said with a heavy sigh. "but I know where I can find her."
Ruby Rose was laying face down in her bunk, crying softly to herself. Her life was over at this point, she had blown everything. Weiss had heard the terrible, awful truth and now things would never be the same. She would never respect her as the team leader or she would ask to be transferred to another team or drop out of Beacon entirely. And it was all Ruby's fault.
A gentle knock on the door broke her from this fit of self-loathing, followed by the sound of the door gently opening.
"Whoever you are, if you came to talk to me, please leave. I just want to be alone right now." Ruby said between bitter sobs, not bothering to look up from her pillow.
"Ruby, it's me," Weiss said softly.
"If you're here to call me a dolt and chew me out, the door is that way." Ruby babbled, pointing towards the door. Weiss gently closed it and, with a stubborn huff, climbed up the side of the makeshift bed to sit on the far end, by Ruby's feet.
"I'm actually here to ask if you want to dance."
"...what?" Ruby said, lifting her head up. The makeup that Blake has so meticulously slaved over for Ruby was smearing and streaking. "Is this..a joke?"
"Far from it," Weiss said with a surprisingly friendly smile. "I just came up here to see if you wanted to dance with me, right here, right now," she said, before using a glyph to land on to make jumping from the bunk easier.
Ruby sat up with a pitiful sniff and wiped some of the smeared mascara from her eyes, only smearing it worse on her cheeks.
"R-really? A dance? With me?"
"I know you can be a bit thick sometimes, Ruby Rose, but I know you're not hard of hearing, Now, do you want to dance? Yes or no?"
"YES!" Ruby said in excitement, leaping down. She was so painfully close to Weiss that she could smell the alluring flowery scent of perfume. "But, um, I don't know how to dance. At least, all polite lady dancing." Weiss laughed at 'polite lady dancing' and placed her hand on Ruby's hip, making the team leader blush.
"Here, see how my hand is? Do the same with me. Excellent. Now, hold my other hand like so," Weiss said, interlocking her fingers with Ruby's free hand. "and follow my footsteps."
And so Ruby did and for the first time in her life, she did 'polite lady dancing', her silver eyes mesmerized as she followed Weiss across the dorm room floor. They dance in silence for a few minutes, before Weiss put everything to a stop. "I believe that's enough for now, Ruby. My poor toes can only handle being stepped on so many times."
"Oh, I'm sorry, Weiss!" Ruby apologized, bracing for the eventual verbal dressing down, but Weiss just gave a casual shrug.
"We'll just have to practice more. Are you free this weekend?" she said, acting as if such a question was a normal, everyday thing. Ruby merely blinked in disbelief, taking a moment or two to process what was just said.
"Did you...? Are you asking me out on a date?" she finally said, her voice barely above a whisper.
"I'm asking if you would like to spend Friday night with me for dinner and a movie, so if that's a date, then yes," Weiss said, her cheeks starting to get just a tiny shade of red.
"...yes, Weiss. I would love to."