I can see how it's a betrayal from that point of view now especially considering it's the last few months before the MC would of gone to college, so she should of wanted to spend time with him and then leave.I don't think MC's true feelings really matter. even if he wasn't in love with her at the time, it doesn't change the fact that they are best friends. they spent every second of their free time together for years.
abandoning your best friend, cutting him out of your life suddenly without warning, not even waiting a few months to be able to leave together, it is a betrayal of their friendship.
they don't have the boyfriend/girlfriend label to their relationship, "only" best friends, so as a real friend, MC supporting her decision as much as he can makes sense, as it is about her dream and her grief over her grandmother. he can only ask her to wait for him. he cannot fight for her as "just a friend".
and then she comes back without any warning, showing up on his door step, as if nothing happened, wanting just to "unpause" the relationship.
i am also of the forgiving type, and i always leave the door open for people to come back. it doesn't mean that things will be the same when they come back. you can be friendly but something is always lost. especially if ties are cut off for a long time.
like someone said earlier, she should feel very lucky that MC invites her to parties and to hang out at all.
One thing I will say I will give Zoey the benefit of doubt about just showing up out of the blue acting like nothing happened. As I swore I recall she did try to call him or text him but the MC changed his number and never told her. So that's why she just showed up.
Yeah Zoey knowing his true feeling probably just wishful thinking on my part and thinking it would of stopped her from ghosting him. But actually would of made it alot worst if she did ghost him still.