Kathy is an adult. Kathy is intelligent. Kathy runs the family home. Kathy most likely has hours in a day when Eddie is not at home, where she could flee with the children. Kathy could make an anonymous phone call to the police.
I believe Kathy is emotionally trapped. I don't even know if Kathy realizes that she is trapped. Kathy is an adult survivor of severe childhood sexual abuse. My opinion is that Kathy is paralyzed by a combination of things: Eddies controlling nature, Kathy's twisted biblical views, and Kathy's personal history of childhood sexual abuse. For the sake of her daughters, I pray she finds the courage to break out.