All In a Day’s Work
It sounds to me like your sister is where she wants to be. She is obviously getting something out of it and if she would rather go through this than work that is her choice. Although it seems silly to me. There are a lot of different jobs out there. She is bound to find one she likes or at least can tolerate.
Who knows she may meet her next horribale but wealthy husband at her next job. This may have more money and be an even bigger jerk. She wouldn’t want to miss the chance at finding that catch would she? Or maybe by some miracle she will realize work is better than being treated badly.