She's a people pleaser, great use that to get her to start doing things to improve her self esteem.
First step is get her to acknowledge her LSE. If she can't see it at this point, she might never. After she admits to what is going on ask her if she wants to do something about it.
If she doesn't want to improve her self esteem it's best to cut the relationship short-it's already starting to affect your life.
If she does get her to agree a couple of times. For example 'do you want to improve your self esteem?' 'yes' 'do you?' "yes" "are you sure?" A lot of people just respond yes without really thinking about the question. Asking her three times helps sure up her answer.
From there, teach her how to have high self esteem. There are tons of articles on this and here's another one
"How to Love Yourself"
Two things will be key for her: 1. standing up for herself and 2. getting out of her head
The standing up for herself will be difficult because of her father but she will eventually get the hang of it. it's impossible to have high self esteem and be a human punching bag.
If you know how to stand up for yourself when people treat you not so nice it should be easy to teach her. Have her sit down and think about all the times she should have stood up for herself but didn't, then start doing it.
You can practice with her at home as well. Tell her randomly that you are going to give her a tough time and give her an opportunity to stand up for herself. Don't make it too exaggerated so she knows when it's coming.
One day freak out over something that isn't a big deal. If she forgets to take the trash out or whatever start yelling at her. If after a minute she doesn't recognize what's going on stop and tell her what you were doing. Then give her some pointers as to what she could do to stand up for herself.
If you do this a couple of times she will start to build up some confidence in herself that she can not take other people's crap.