
I agree, and if I remember correctly, before she got reincarnated, her modern day family abused her too. So in this life and her last one all she knows is abuse. With her brother, he's a lose cannon that's easy to displease and when he gets triggered the punishment is worse for her. She doesn't know how to fight back or have anyone in her family to turn to, so all she can do is act like a doll and pretend to be happy with him. And because of this, she doesn't know how to accept help either. She thinks getting abused and being bulimic make her unattractive and dirty so she thinks the only way to keep Iz around is to hide everything. It's really tragic.
The heck?! Keeping up appearances with your brother is not even preventing you from the most dreadful thing!!! Thats so dumb.. I know she got trauma but like, thats so pointless!