Here's an autistic tinfoil hat theory: Maybe Eugenia's catering to the fetish watchers in a sort of way by getting fillers, while also doing it to perhaps portray some weird illusion of health as a kind of defense against outsiders becoming concerned with Eugenia's health to a point where she'll be 5150'd again. It's hard to deny that she looks childlike: the way she dresses, the way she behaves, her likes and dislikes, and even the way she talks is all sort of childlike. If she had the sunken in cheeks of the Lich Queen, perhaps these suspicious ass people wouldn't find her to be as attractive.