@mommunism what do you expect her to do? get a job and move out? she doesnt exactly have many options. sure she could run away to her husband and daughters house, but her "mom" will file for a missing child, what happens when they find her clearly with the other two....obviously it wont be good for them and obviously they wont be able to convince society shes a actually an adult women.
the best she can do is call child protective services herself, which could work, but her mother so far only seems really strict and untrustworthy of people, not exactly abusive,so until we see more, i dont know how much that could work
(or how effective child protection services even are in japan)