A/N: SO this was originally a prompt, this one:
Hey! I LOVED your co-stars AU! SO adorable! So I have a thing about the trope 'Best friends who are in love with each other' Could you please possibility do a prompt with that?
AND after so much support I decided to make it a multi-chapter, however bare with me as I am juggling a lot lately. And hopefully posting this will push me to update... So enjoy...

She sat at the bar, a glass of wine in hand, lost in her thoughts; she should be happy. She was happy; her best friend had just proposed to the love of his life, but all she had was this nagging feeling in the pit of her stomach.

"Penny for your thoughts?" A male voice cut through, she glanced up at the soft features of Tommy Merlyn.

"Hey Tommy."

"You okay?" She watched him as he sat on the stool beside.

"Are you okay?" She countered with an easy smile.

"Why wouldn't I be?" He flashed his trademark smile but she could see it in his eyes, see the pain, and see the true feelings deep inside.

"You know why." She turned fully to look at him, her arms crossed over her chest. He just stared at her blankly. "Don't pretend to me Merlyn, I know your secret, remember." She raised her eyebrow. He closed his eyes then taking a deep breath.

"I know." He replied sadly not looking up at her. "I've well and truly lost her."

"Hey, you always have me." She said placing her hand on his arm. He glanced at her with a soft smile.

"And you've got me too you know." She smiled at him. "And I know you'll rebuff it, but you must be feeling pretty rough too."

"I'm fine." She lied pulling her hand away.

"You might deny it all you want Smoak, but remember I've seen the way you look at him." She sighed then.

"Yes well it's all too late now Tommy." He nodded unable to say anything to her, to make her feel better when his own heart was aching. She reached out for his hand on the bar squeezing it lightly, as he did the same, both finding comfort in the others touch. A cough caused them to pull apart, and the pair was met by the eyes of the happy couple.

"I didn't know you two were dating?" Laurel said with a surprised, yet coy grin.

"Oh we-" Felicity started before Tommy cut her off.

"Congratulations you two!" He stood up pulling Oliver and Laurel into a hug, Oliver's eyes never left Felicity as he frowned at her. "Oh, and happy birthday Laurel."

"Thank you." She smiled gratefully.

"Can I have a dance?" He directed at her before he turned to his best friend. "All right if I have this dance with your lady?"

"Of course." Oliver said with a smile stepping away from Laurel as the pair walked to the dance floor. Oliver sat down on the seat that Tommy had just occupied.

"Congratulations." Felicity said softly staring into her wine.

"Thank you." He replied. They sat in silence for awhile, a strange feeling of awkwardness over taking them. "So you and Tommy..." He left the sentence hanging in the air and she snapped her eyes to his.

"Me and Tommy what?" She said tilting her head.

"I just… I didn't think he was your type." He shrugged and she laughed.

"You think you know my type Oliver?" He froze for a second, unsure what to say.

"I just don't want you to get hurt."

"What and Tommy is going to hurt me?" Oliver said nothing as he stared at her. She sighed heavily. "I can take care of myself Oliver; I don't need you to protect me."

"Felicity..."

"No okay? You're my friend and I'm happy you're happy, I really am. But you don't get a say in my love life... You have no right." His mouth hung open and he frowned.

"I'm not... I just you're my best friend Felicity..." She closed her eyes then, those words hurting her more than she ever thought they could, meaning more to her than he ever realised.

"I know that... I've known that for a long time." She never looked at him.

"What's that supposed to mean?"

"Nothing." She replied finishing her wine.

"Felicity I just... I remember the last time your heart got broken." Suddenly her eyes flashed to his her heart pounding in her chest. No she needed to forget that, she needed to get out of there. She stood up and he frowned at her, his hand sticking out to steady her as she wobbled slightly. She took a step back away from his hands; his face fell slightly before returning stoic again.

"I'm not feeling so well... I'm going to head home. Apologise to Laurel for me and congratulations again." She grabbed her purse span on her heels and headed towards the exit.

"Felicity..." He called after her but she never stopped, never faltered until the cool evening air hit her skin and a tear slid down her cheek.

She told herself that this was her own fault that she knew deep down she was never really over Oliver Queen. She sighed as she walked down the street lost in her own mind.

5 years earlier.

"Fliss..." She closed her eyes letting herself sink to the floor, her back against the door. "Please Felicity let me in." She didn't want to open the door, didn't want to hear his fake apologies, and didn't need to hear it. She knew now she was a fool.

"Get the hell away from her door." Another male voice snapped her eyes open.

"This is nothing to do with you Queen." Suddenly she heard a thud against the door and Cooper groaned in pain.

"This is everything to do with me." She heard him threaten him. "Now get the hell out of here Cooper, and if I ever see you again so help me I will call the cops myself." She heard him drop to the floor. "In all honesty I don't know why she didn't grass you up already!" She heard someone scurry away and then a gentle tap on her door. "Felicity it's me he's gone..." She couldn't move she was frozen in place. "I'm not going anywhere, I'll be right here when you need me." Slowly she pulled herself up unlocking the door, and opening it an inch.

"Oliver..." She whispered and his heart broke when he saw the tears down her face, her eyes red and puffy. He opened the door wider stepping in and she threw herself into his arms burying her face in his chest as she sobbed. He kicked the door closed, and wrapped his arms around her, gently rubbing a hand up and down her back to soothe her. She felt her heart skip at the tenderness he always showed her.

She'd tried to ignore her feelings, but as the years of their friendship had grown, the stronger she felt them, but he had never shown any signs of wanting her. They talked, they laughed but that came from growing up together, nothing more. Much to the disappointment of Felicity's poor heart. She tried to move on, purely from enduring watching him go from girl to girl. But the only other man she trusted with her heart had just shattered it into a thousand pieces.

"Hey I'm here..."

"I'm sorry." She whispered into his skin.

"What are you sorry for?"

"I should have listened to you..." She pulled away from his chest then, his arms still around her.

"Don't do that to yourself."

"But you were right-"

"Felicity, it doesn't matter. You liked him and you trusted him, he broke that... And I'm sorry you have to endure this heart ache." Her bottom lip quivered slightly and he wrapped her in his arms pulling her closer again.

They spent the night watching films, her sobbing coming and going but Oliver never left her side. They spoke and they didn't, then in the early hours of the morning she felt her already heavy eyes falling closed. He gently lifted her placing her under her sheets, he took a step back and her hand wrapped around his wrist.

"Don't leave me... Please..."

"I won't leave you, I'll be right here on the floor..."

"No," she pulled him closer, "we can share a bed like when we were kids... When we used to have sleepovers, you, me and Tommy remember?" He smiled.

"Felicity." She opened her eyes then.

"Please." She watched as he sighed deeply kicking off his shoes and suddenly he was sliding under the covers too, wrapping his arm around her. She curled into his side, her black tank top rising up and her soft skin so warm against his hand. He stared at her dark hair with purple streaks as her breathing slowly evened out, he knew she was asleep and he closed his eyes too.

When Felicity woke up she could feel her legs tangled with someone's, a hand on her bare skin drawing lazy patterns. She was hazy but she knew from the feel of him that this was Oliver. He had stayed and suddenly it hit her, she wanted him. She slowly glanced to his beautiful face, his eyes were closed, but the rays of light made him look picturesque.

Her body seemed to act of its own accord, her brain completely blank as she stretched up placing a kiss to the underside of his jaw, then to the corner of his mouth over his mole. He hummed, his hand on her side squeezing a little tighter. Then she kissed him on the lips, her eyes snapping closed as she let the sensation of his lips on hers wash over her and to her surprise he kissed back. She moaned and his tongue swept through her mouth.

His hands fell to her ass lifting her slightly till she was lay on top of him. Her hands threaded through his longish hair, scratching at his scalp, his groan spurred her on and suddenly he sat them up. She could feel his erection through both their jeans pressing exactly where she needed him. She ground down and she felt his hand cup her breast. Both were completely lost in the moment lust taking over their senses. She moaned loudly pulling her lips from his.

Suddenly the ringing of Olivers phone snapped both their eyes open. She could feel it vibrating near her leg and her brain finally caught up with the situation. She was kissing her best friend, practically dry humping him and as if cold water had been poured over her she literally threw herself across the room.

"Felicity..." He said softly. "I'm sorry..." He continued and she frowned. "I shouldn't have kissed you back, I should have realised this was a bad decision." Her heart broke even more at his words. She glanced down, trying to stop the tears. He pulled the phone from his pocket. "It's Laurel I have to take this."

Her mouth fell open, crap he was in a relationship; well technically he wasn't as they were on a break, but still. She nodded to him, his lips still swollen and the bulge in his pants, well bulging. He slipped from the bed pulling on his shoes, and then headed to the door before turning slowly towards her where she still hadn't moved.

"I'm sorry..." She could hear and see the regret oozing from him and all she did was nod. As soon as the door clicked shut behind him she fell to the floor.

The realisation finally hit her all at once: She was in love with her best friend. She was in love with Oliver Queen.

And he clearly didn't feel the same way; this was bad, really bad. She closed her eyes. There was only one thing to do, one way to protect her heart from more pain, cut him out of her life completely.