This is very true. I was trained by my parents to be a people pleaser and I struggle. My 15 yo dd is very strong willed and has a tendency to try to control me and I have been caving due to illness. I get what it is to be ill op. I’ve been chronically ill for most of dd’s life and her controlling behaviour stems from this, when she was little and scared of the sudden realisation she has an ill mummy.
I understand you are scared and confused. Your ds has confided in you because ultimately he wants and needs your help. I totally disagree with your dh’s approach btw. Young people, who haven’t had good boundaries imposed or who are trying to work things out for themselves make a lot of mistakes. If this young woman is loving and caring yet violent and moody, she is a product of her environment. Not that you can excuse this. But maybe if you show her better, she will do better.
You have had various suggestions of how to deal with this. If you don’t want to go one way or the other, you could go for the middle ground. By this I mean to talk to her in a kind and gentle manner about how you get she had a hard time from her parents. And ask her if she thinks this is a good way to behave. Ask her if she wants to hurt your ds, what she’s trying to achieve.
The response may surprise you. She may actually be looking for him to hurt her as that’s what’s she’s used to. The next question then is what if he never hurts her back, is she going to escalate in the hope that he does even if that risks serious harm or death.
If I felt I could do this and not be in danger, this is the approach I would take as it is giving her and your ds a chance to work through this / past it / split up etc.
A very different example, I know. But I recently spoke to a boy, who’d really hurt my 15 yo dd. I was talking to him and his mum about something else, some information I needed due to my dd’s medical condition and it seemed like a good opportunity to let him know how he is being perceived by the girls at dd’s school and how he’s using girls. No details required really but I did this to protect girls in general as well as himself as he’s all over the place emotionally and love bomby. I was gentle and and non accusatory and he seemed to take it very well.
What I did took a lot of courage btw. I was in their home and I had never met his mum before, only spoken a handful of words to him. If you do talk to your ds’s gf, you will be in your home. And you can ensure you do it when your dh or another person, who you trust to protect you is around even if not in the same room.