I agree with most of the opinions here about the Ava situation. It's a weird situation that has changed how I think of her role from Chapter 1, I was interested in how will her role as a cheater will play out because I was interested to see how I would react to remorseful cheater as an LI. But, now I feel nothing on her role but that this unnecessary baggage for the both of us, more depressive thoughts for the Mc to have to deal with and for Ava redemption and overcoming her trauma's and fear of others.
For Annie, I still don't see her in that much of a negative light yet, but I'm afraid that won't be for long depending on the future reveals for her reason for the trip. Maybe it's because I think I need a person like Annie to make become "normal" again by becoming more socially active, but that's beside the point. I think the reason for her to become that angry after hearing Ava's story is that she believed that Dick and Bryce are that much of scumbags that would do something like that, so she believed her story and she wanted to us hear her story because she thought we would as well.
Now the problem I have with the story is that I'm almost certain that the Bully bros aren't only going to be shown in the flashbacks. I believe that the trip Annie is making to NY to meet Dick and try to get back together, so she can try to help her parent's economic problems. I say this because the two major LI's we have would have a clear character arc that involves getting revenge on them.
Now the last thing remaining to solve is who is her what that means for the MC's character arc, depending on who she is it would have different meanings. If she is MC's mom it would have to do with the financial ruin that happened to his family, and as result, his Mum overworking to death as a result. On the other hand, it could be a LI that has died, but I wouldn't expect because we are made to believe that since Annie and Mc started Uni they haven't had the same relationship as before as she didn't know that much about Ava, and it seems Annie knows all about "Her" and the impact of her death(?) had on the MC and lastly Annie's Mom knows about it as well (her, on the other hand, could be referencing to what happened to MC's family) so it can't a Li in my opinion. If the assumption is correct about Her being his Mom then I'm Bryce and Dick's family will have some involvement as well on this plot as well.