within the limits of the narrative Zoey thinks about home in general and MC in particular at least until the stupid choice to let him go (she wanted him to go to San Diego when she had to finish school, then when school is over she doesn't want him anymore..), and by that time surfing is already a failure.
But it takes courage to reintroduce yourself to someone after deliberately avoiding them, and Zoey only finds this courage when she has no other options
i overall agree with your perspective regarding Zoey in the interlude. i think it was an overall small failure on DPC's part regarding the way she is written. if he really wanted us to believe she was homesick, then why wasnt that more prominent throughout the entire episode? why emphasize that she only comes back home when she has no way to survive in San Diego?
im literally gonna pull something out of thin air that could have been added in: have a scene where Zoey wakes up from a dream about a past memory with MC (like hanging out in detention or whatever). we dont even have to see the dream, her inner monologue can make that apparent for us. then as she lays in bed thinking about the dream, maybe she picks up her phone and looks over the last texts she sent MC and has a look of worry/contemplation as she thinks about texting him again to see how is has been doing. ultimately she doesnt have the courage to send anything, but at least its made clear to the audience that she considered it and maybe actually has mixed feeling about MC and how it ended.
but instead of stuff like that littered throughout, she spends her days having a total blast and spinning around in chairs and living her best life with MC not even a thought in the back of her mind for 99% of it. DPC could have let her wear that mask in front of her new friends, but in her alone time we should have seen much more of her vulnerable insecurity and mild despair at her situation with her "best friend". and as ive previously mentioned on this topic, if you had her ACTUALLY DATE people as she pretends to "move on" (pretends is because she obviously stays an option to MC based on the nature of this game) and realizes through personal experience how shitty so many other guys are, and then as a consequence realizes how great her and MC were together and that she now knows she wants their relationship taken to the next level. that makes a much more meaningful catalyst for her returning home, and it would make sense whether she had money/success in San Diego or not, and doesnt add any negative connotations to her character motivations for returning.
i think many of the Interlude's issues come from the differences on how the game was set up to played compared to how its supposed to function merely as a larger slideshow of filler information to catch her up to everyone else in the game's timeline. if the game was built to actually mimic BaDIK and Zoey was a real MC of her own, with us being able to take many different paths as she experiences genuine trials and tribulations (including sexual encounters), then her journey and growth could be better explored similar to the actual MC. but because she is like some psuedo-MC wannabe in her episode, it limits what's possible for us to experience when "playing" as Zoey, as well as the fact that she reverts to basic side girl status in the real game means that the mish mash that is the Interlude just doesnt really work particularly well in any of its intended roles in this overall story.
