I'm going to reply to this not as a witch, but as a social worker (which I am).
First of all, I think it's really great that you care so much about your friend and are wanting to help her. That's awesome; it sounds like she needs a LOT of support right now.
The behavior of her parents is unacceptable; no human being deserves to be treated like that. Period.For some non-witchy ways to help her, I want you to try to step into her shoes for a minute, so bear with me through this upcoming novel.
These are her parents. She literally would not exist without them, so leaving them and possibly cutting off ties would probably be really hard for her. She might feel guilty, like she owes them something, or maybe that she's betraying them in some way. And, like almost every person, she probably genuinely loves her parents. Which she should; it is absolutely okay to love someone who abuses you, you can't just flip a switch and stop loving someone. That's part of the reason it takes a victim of domestic violence, on average, 7 attempts to leave before actually leaving their abuser. It's usually a really slow process. Researching domestic violence might be helpful for you in this situation.
Another thing to think about is where she would go if she chose to leave. If she doesn't have a means of transportation or a job, then I'm guessing she probably doesn't have enough money saved up to pay rent. So she would be staying with different friends, probably moving around so as to not impose on any one person for too long. If you don't know, this is called couch surfing and is technically homelessness. So, if your friend leaves this awful situation, she would be putting herself into homelessness and a really uncertain future. I've couch surfed before and it's scary. It takes a HUGE emotional toll and often comes with feelings of guilt and worthlessness (I work with homeless youth and see this all the time). So even though your friend has offered to take her in, she might not accept the offer because she wouldn't want to be a burden.
Quote:
She's told me and our other friends all about the kind of treatment she gets, but without even realizing how bad it is herself.
If this is all she knows, then chances are she doesn't know what a healthy family unit
should look like. Maybe, to her, this is normal so she doesn't understand what you and your friends are trying to tell her.
Keep in mind that I don't know the situation as well as you do, so there may be other things going on. These are just my educated guesses based on what you've said
Some things you could say that may be helpful are:
"It's your choice and I completely respect that. I'm here for you."
"I get that you love your parents, and that's okay. Look at what this relationship is doing to you though. It seems pretty unhealthy."
"You deserve to be treated with dignity and respect."
Help her to find her worth and her strength, let her see what a healthy familial relationship should look like,
don't pressure her to leave, and just be there for her. I know these things might not be as action-oriented as you might like; it's really hard to see someone you care about go through pain. You've just got to remember that this is not your path to walk; it's hers. You can walk next to her, but you can't lead her.
It sounds like you are a pretty amazing friend and are doing a lot of things for her. Just keep being there for her and don't forget to make sure you're okay through this journey as well.