I think the author kinda falls flat on that. They hinted at her being the way she is due to an eating disorder, and I doubt they'll be able to go through what someone dealing with an ED does if they wanted to acknowledge and fix it as a disorder for the remaining chapters. Kinda ironic after her whole spiel of not judging them based on superficial characteristics, she goes and ends up in the same cookie cutter mold of acceptable proportions (it feels weird, but i think they'll atleast make it something she wants to accomplish, so there's atleast a logical reason for her change).
Id imagine if there was more to this than 10 chapters, they'd introduce a character who starts and ends as fat and happy.