Based on this prompt from klarolineishot on Tumblr: "Felicity helps the ATOM like she does for the Arrow team. Oliver learns and gets jealous and possessive. 'But we're partners.' or 'Aren't we Team Arrow?'"
I'd like to note that I am a cruel bastard and that I have not read any spoilers about the coming episodes. I'm sure this isn't what's going to happen, but I kind of think Felicity should leave the team.
When Felicity leaves him standing in the alley, hating himself but unable to think of another course of action, Oliver thinks he just might be able to survive losing her. Maybe they won't be together like he imagined, like he needs, but at least he'll still see her. She's always been committed to the cause.
So, when she doesn't come to Verdant the next day, it feels like being kicked off a cliff all over again.
"She's not coming," Diggle explains, voice full of accusation. "She's helping Palmer now."
Oliver turns and leaves without another word and drives straight to Queen Consolidated. He knows it's not called that anymore, but he can't admit that to himself at this particular moment. He's not technically allowed in the building without an invitation anymore either, but he became rather good at sneaking in and out of his office during the time he was running the company and he gets onto the executive floor without detection.
He finds them standing at a table, heads together as they talk about the various mechanical parts strewn before them. They turn to each other excitedly and smile and Oliver suddenly remembers, quite vividly, the last time he saw them here together.
Felicity spots him out of the corner of her eye and turns to face him, her expression going cold and angry, and Oliver feels ashamed, insignificant. She turns back to Ray, rests her hand on his arm in that way Oliver knows so well and says something to placate him before she strides over.
"What do you want, Oliver?" she asks, no time for niceties.
"Why aren't you at Verdant?" he asks, trying to sound angry and feeling like a petulant child.
She sighs in annoyance and crosses her arms. "I thought I made it pretty clear how I feel about your decision to work with Malcolm Merlyn," she says. "I won't be a part of the team if he is."
"Felicity, I can't defeat—"
"I don't want to hear any excuses," she interrupts, holding out a hand and closing her eyes in frustration. "You've made your choice and I've made mine. I hope he can help you beat Ra's," she adds and turns away.
Oliver wants to run after her, to fall on his knees and beg her to stay, but all he can manage is to say, "But we're partners," though it sounds like "I love you."
She stops mid-step, shoulders tensing as if he's struck her. He sees Palmer through the glass, looking concerned as he looks at her face, taking a step toward her before she stops him with an infinitesimal shake of her head.
She exhales, her body relaxing as she does. "Not anymore," she says without turning around and then walks away.