Disclaimer: I do not own the characters or the show. They belong to freeform.
Mariana wasn't blind that's something that was for sure. She noticed things despite acting like she didn't care she still watched everyone especially her siblings. Despite being wrapped up in her own world she still saw what was going on around her especially when the changes were obvious. A change in Callie for example that was very obvious to the Latina. Her sister had been so stressed lately between figuring out school, fighting for Ximena and her break up with Aaron she hadn't been in the best place lately. It wasn't all at once that Mariana noticed a huge change, it was more like a gradual build up.
The Latina first noticed a change in Callie the day she made Huffington Post. When Callie came home from the church it was as if something was different. She watched as her sister walked into their room appearing to be very tense but almost giddy in a way. Mariana didn't address it, she just silently watched as her sister didn't seem to know what to do with herself whilst she made small talk with Poppy. That wasn't the last time she saw a change in Callie. After every visit to the church Callie appeared almost content with life and that was a rare look for her. She seemed to be happy almost. Mariana had a feeling that someone was making Callie happy but she wasn't ready to make any assumptions yet.
Callie cared for Aaron, Mariana knew that much for certain. What she didn't know was why she bothered with him. Mariana noticed a big change the night after her sister went to Aaron's place. She appeared to be hurting a lot but again Mariana left it alone being the casual observer that she is. Still though the Latina wondered what had happened. It didn't seem to take Callie long to get over it though. One talk with Ximena and her sister appeared alright again. Not fixed but at least not upset anymore.
When Ximena moved in Mariana started to notice some things the first being the staring. Ximena tended to watch Callie a lot, at first the younger Latina thought it was because she was worried about her sister but then she watched more. She noticed that the look in the older girls eyes wasn't just one of gratitude, fondness and worry but one of dare she think lust. At this point Mariana's theory grew that Ximena had feelings for Callie but she wasn't sure just yet. The younger girl started watching her sister more closely then. She noticed things she missed before the way Callie glances at Ximena too with such caring eyes. The other thing she observed was how they could find each other's eyes instantly at any time. The whole thing only made Mariana more curious about the two girls.
The next thing that Mariana noticed was how they were always touching in some way. It wasn't always obvious, honestly she thought you would really have to be looking for it to even notice most of the contact. At the table the two would either be seated across or next to each other. When seated side by side they'd have their legs rubbing against each other's, when across from each other they'd have their lower legs touching under the table. The contact was still there, subtle but there. When they would sit in the living room the two girls with sit side by side, Callie would curl up next to Ximena, the older girl placing a protective arm around her while they enjoyed a movie with a blanket covering both of them. There were times that Mariana could have sworn that they were holding hands under that blanket but she couldn't be certain. When the two were in Callie's room they would sit or lay side by side on the bed hands casually touching each other's arms and legs constantly. Legs always brushing together. Everything looked so carefree when it came to them together. Laughs always ringing out periodically, Callie appeared happy and that made Mariana happy. The contact was what made the younger Latina believe that Callie may feel something for Ximena too but she wasn't certain just yet.
Mariana finally got her answer when she came home early from school one day. She was not aware that Callie and Ximena's art class had been canceled so they were home. She was made aware of their presence upon walking upstairs and hearing giggling coming from her room. She paused just in view of the doorway but neither girl noticed her as they were too wrapped up in each other. Just as the younger girl was about to make her presence known she saw Ximena lean in and kiss Callie. She watched as her sister pulled away in was she thought was confusion but instead of questioning Ximena Callie just smiled and kissed her back. At that point Mariana decided that she would leave and come home later. She couldn't bring herself to interrupt their moment together. At this point she was pretty certain that her sister and Ximena were together or at least on their way to being together. This thought made Mariana pleased as she couldn't have thought of someone better for her sister then Ximena.
The Latina got her real confirmation about two weeks later when Callie asked her if they could talk in private for a bit. During the heart to heart Callie came out to her sister and reviled that she was in fact dating Ximena. Mariana just gave her a knowing smile and said that she was happy for her and didn't think any differently of her. Mariana was happy that she figured it out and was glad that her sister was finally feeling comfortable with herself. If Ximena made Callie happy who was Mariana to stand in their way. After that conversation Mariana noticed her sister an Ximena being more open around her, especially in the sisters shared room. They even went as far as to share a few short kisses in front of her and every time the younger Latina would smile as she was so thrilled for her sister's happiness.
About three weeks after Callie came out to her she called a family meeting that Mariana could only assume was to discuss her and Ximena's relationship. After a very emotional family talk about her sexuality with Ximena by Callie's side the whole time she finally reviled that the two were dating to the family. Some congratulated them while others gave them a knowing smile Mariana being one of the latter. She gave her sister a hug and reminded Ximena not to ever hurt her big sister even though she knew Ximena could never do that to her. The two shared a quick kiss and bid everyone a farewell as the newly out couple left to go and work on their art. It's a good thing Mariana isn't blind because the signs were all there, it was so obvious looking back on it.
Authors Note
Sorry about the lack of updates for Instability. I was super busy with school and work but I have more free time at the moment to get back into writing. I needed some inspiration so I decided to write this chapter of a new multi chapter fic I've been really wanting to do. I'll be attempting to update this as frequently as possible. Might knock out more chapters since I'm motivated to write this fic. Going to try and do weekly updates with my other fic from now on, maybe more if I feel inspired. I hope you enjoyed.