This happens to a lot of events, not just Zoe. I feel like the events themselves need a bit of tweaking cause some players, myself included, are almost certainly going to focus on one character at a time and it makes certain events soft locked. I would suggest using those moments when the house mates aren't home doing who knows what to also function as a way to indicate that you should interact with certain characters before they can continue or at the very least make the events more forgiving in terms of the prerequisite or if you've long passed the prerequisite just let it play out anyway.
Viewing post in The Dorm House - WG, BE comments
I have a future solution for those that don't want to force a character to lose weight to see certain events, but I wanted to avoid having situations where say, Zoe is at stage 4 in your game, but suddenly an event triggers where Zoe is stage 0. I feel like that breaks the immersion a bit too much.
Also, take the Becca/Lily bra shopping as an example. I created unique sprites for them for that scene at specifically those stages; they wouldn't quite match up at any other stage.
I plan on using the Movie Theater to let players purchase events that are technically "missed" (I.E, a Zoe stage 0 event with another housemate at a higher stage), as an alternative way to view content, if you don't want to have them lose weight. The Zoe issue is a genuine game breaking glitch though, I'll need to block Zoe from being able to lose weight before the player goes through all of the restraint brew events.