Thanks for all the advice and different views folks. After giving it further thought, I think I'm in a lose/lose situation here. I either say nothing and deal with a life of being insulted, humiliated and controlled by her Mother in particular, which I think will lead to arguments, tension, distance between us, and a break up, as per the ex husband, or at the very least, a miserable life for me based on the last six months, or I try and address it, in which case, as some have pointed out, I come across as controlling. I can't win except to break up. I just want a normal life, really. I'd sooner be alone than be in this blender of madness, life is too short.
For those who say I'm trying to control my partner, it really hasn't ever been about that. I couldn't care less about her seeing/interacting with a normal family. Genuinely, hand on heart. Couldn't care less. I just can't sit and pretend her family aren't abusive. I can't condone it. I'd challenge anyone who thinks this is about control to spend six months in the same position as me and reach any different conclusions about them or interacting with them. This isn't just about me, it's about how they treat her, whether she was with me or not. I'm not trying to force my opinion on her, she talked to me about it and we seemed to be on the same page re: how to deal with it. I can only take her at face value and try to move forward. This isn't a situation I've engineered to suit any agenda of my own, I've spent six months giving them the benefit of the doubt and trying to make it work, for all parties. Yes, she's free to make her own choices, but equally, I can't pretend I think it's healthy to let someone behave appallingly to both herself and me, and then not hold them to account, and equally, when my partner tells me she's on the same page as me with all this, then seemingly isn't, it's disheartening and frustrating after sticking around. I don't want any medals, but that's just the reality of human emotions. And why would I want to share my life with someone who'd let her family treat me like that? I'm being told by her that she doesn't think she's strong enough to stand up to them on her own, I don't know, I feel I've been painted into a corner where whatever I do I'm going to be the bad guy.
Anyway, it's always good to hear a view counter to your own, it's healthy to challenge your thoughts with another viewpoint. So thanks to all. I won't be dealing with this any longer though, enough is enough.