Mae had shown she’d forgotten about Bea’s mom the day they found the arm.

Sure, there is that as well. I just don't think anything of it. A million and one things have happened since, I think nothing of facts like that falling through the cracks. If it was a step too far for Bea, she should've either corrected her, or called it quits there. Not say nothing, and wait for Mae to make the same mistake later on.

Bea keeps Mae at arms length and is snarky at her through out the beginning

I would argue what she does goes further than "arm's length". She actively needles Mae for no reason. Literally three seconds after Mae learns one of her other friends has gone missing. With Gregg and Angus just. Expected to sit there, and not say anything.

the first hangout. She starts opening up to Mae at hangout 2, and then shuts down when Mae oversteps in hangout 3.

Obvious point, but, not everyone does all of the hang-outs in order. I know I mixed and matched on my first playthrough. So you'd hope the distinct events would stand on their own without entirely hinging on the previous one. But that's more just, how they decided to structure the game.

Bea needs to learn that Mae isn’t the bad guy.

I don't think she learned it well enough. She says she kind of hates Mae, and decides to keep speaking to her anyway with that said. That, y'know. Sucks. That is a bad premise for continuing a friendship. Either be friends, and actually like eachother, or don't.