Here's where I'm at, and it kind of does mirror what many has said before.
Whatever happened, which we don't know yet because it's clouded in mystery, that's irrelevant to me as far as me seeing her a a love interest goes, I don't see her as one anymore, and here's why;
1. She went to a party despite MC asking her not to, knowing full well Bryce, who bullied MC back in the day would be there (and if I recall, she used to crush on Bryce back in the day, and maybe to some extent still does), feel like a bit of a betrayal to me.
2. Despite promising MC not to, she still went and got drunk and high in the party, knowing full well how she can be when intoxicated. Broken promise.
3. Flirting, dirty dancing with Bryce and all that. Gave the impression that she went into the party knowing that she just might end up cheating on MC with Bryce.
4. She took Bryce's hand, knowing full well what would happen when they go upstairs (like, when does it not mean just that when someone asks you to go to an empty upstairs room for privacy in a party).
5. Didn't even tell anybody that she has a boyfriend, let alone that the boyfriend is MC.
Whether something in actuality did happen (cheating or rape), or maybe it was a staged scene (meaning nothing sexual actually happened) to make sure MC and Ava would split as a result, don't matter to me, those 5 strikes I mentioned above means I could never trust her, and trust is key in any type of relationship.
As far as being a love interest goes, she's done.
As for Annie, some friend she is if she's so quick to take a stranger's story at a face value and get pissed at MC without hearing his side of the story first. And how does she know Ava isn't lying, shit, Ava probably doesn't know the facts and details herself either and she's just spewing out anything to make herself the victim and not the villain.
But if Annie is this quick to take a stranger's word and kinda judge MC, her friend based on what may be a cooked up lie, then perhaps she's no real friend after all. And if that's how it is, then I can't see a love relationship with her either.
MC is not a stable person right now, neither is Ava and Annie likely isn't either, each has their own baggage, but it's clear that at least MC and Ava are not good for each other, they both need stability, which is something neither can provide one another, and there's no trust anymore either. They just need to forgive, forget and move on separate ways.