you're pretty much putting it all on zoey. they both didn't define the relationship. obviously she knows that mc wasn't happy about it, she herself mentions it in the dialogue. she's staying happy and upbeat because she doesn't want to put a downer into the conversation. the first thing she does on the train is draw a picture of him, do you really think she didn't have mc in mind? she also suggested for him to come with her so i don't understand why you think she left him, when in reality he didn't go with her. they both understood they had different paths here. the ghosting thing is because she thought she was giving him space to heal, she herself never intended to stop communications until she saw emma and bret's situation."she's not an ex who bailed on the mc." - Of course she was, just because she refused to acknowledge it with the excuse that she's not "good at feelings" doesn't mean she isn't. Just look at how he talks about her and his reactions, he was clearly upset about she leaving (the bench scene) while she was happy about it and even started ghosting him. That's pretty damn lame even if you look at them as just long time childhood friends.
I think my problem with the interlude is that the whole thing is designed to make you feel sorry for her so you welcome her back when in reality MC is the one that got hurt. Seriously, her whole story is based on generating pity and the death of her grandmother is part of it. Everything she wanted went to shit so she comes back crying, it's really hard for me to find her interesting because of that.
the interlude is not meant for you to be feel sorry for her. the interlude was there to show you her personality and to fill you in on "her side" of the story. it was designed to show you her epiphany moment with her life and how she went about it. she shows you how she found her real passion. she realizes what was really important in life and decided to go after that instead of her childhood dream. it generates no pity.
outside of quinn/bella i think she's the most interesting character.