Thank you for articulating this so well. You’ve managed to pin down some ideas which felt very nebulous for me but yes, of course you are right. There is too much risk of physical / emotional harm.

I know I may need to exclude B sometimes, but part of encouraging her to leave is building a separate support network and improving her self esteem which is why I try to invite her as often as possible, even if that means I have to spend time with the horrid partner. But you are right, that is my choice and I shouldn’t expose others to that.

Relocation is not an option, but you are right, when she leaves he’ll know exactly where she’ll be as he’s successfully cut most other friends off. I will start looking into safety plans etc.