I'm team Alexis all the way, but I think we must withhold judgement on Erynn until her perspective of the event has been shown. The exact nature of her relationship with Ethan is unclear but she would have been fully within her rights to reject MC's advances when she did. She was fifteen. MC was twelve. I don't know many fifteen year old girls who would ever consider dating a prepubescent twelve year old boy. She may have developed feelings for him later after having been treated wrongly by Ethan. Her feelings for MC aren't the problem. The fact that she feels entitled to his love is. Just how problematic this attitude is can be revealed simply by flipping the MC and Erynn's sexes.
I never said her feelings are the problem, I said she was a shitty friend who previously rejected the MC and therefore doesn't have any claim over him. But I'm also not sure how she could've developed feelings for MC when she wasn't in contact with him at all. Hell, iirc, MC's MOM wasn't even really in contact with him, so it's not like she was getting updates on him. If she developed the feelings during the five years MC was gone and out of touch, that would mean she fell in love with a fantasy... which is also problematic.
I see some people saying "maybe it's a false memory" but he was twelve... You can remember bigger events that occur at that age. That's (early) middle school age. At best, from Erynn's perspective, we'd maybe see that she scolded what's his name after MC ran off embarrassed/upset, which, to me, isn't enough. Odds are that MC forgot about the Alexis moment because he was so focused on Erynn... Also not withholding judgment on Erynn though because regardless of her relationship with Ethan, she shouldn't have been making fun of MC to begin with, and she shouldn't have been idly standing by when she saw he was upset. I'm all about loyalty in my friendships, and that was disloyal af - even just on a friend level.
However, I think we both ultimately agree that Erynn needs to get her shit together, so that's good enough for me lol