I've done this once, well over a decade ago. He was a mate and I was staying with them. She responded in the the same way as your brother's girlfriend but I don't know how things turned out.
I'm sorry I've not done it since. I think it's because the fallout from that one would have been minimal and more recently I feared losing friends
... Women friends who knew the score and made it clear they would have shunned me not him. I really don't know what I would do if/when the situation arises again.
Arghhhhhhhhhhh!!!!
On the friend's thing. One of my close friends as a teen/early twenties was getting battered regularly by her bloke who was, because of his connection to her all of our friends.
I used to hide her in my mum's house and he'd come looking for her and I had to lie and say she wasn't there...I always thought he knew I was lying.
She stayed with him...Myself and others spent less and less time around them as it was too painful. She convinced me to go home with her for some food one evening saying he was out. He was out but then came home with some arsehole who I know had robbed and raped another friend 6 months previously. I kinda froze in shock...robber/rapist got totally didgey when he saw me...he knew I knew, then he started creating a scene, telling my friend's abusive partner how he was never visiting again as the 'females in your house are too stush and rude'...he basically wound him up into a frenzy then left.
Much slamming doors and ranting...then calling my mate into the kitchen to verbally assault her, then dragging her by her hair into the bathroom to beat her up. He wrapped her long hair around his hands, I could not get him off...everytime I tried he dragged her some more and kicked her. I begged and pleaded with him until he let her go...well he unwrapped his hands from her hair and threw her against the bath.
We sat in the bathroom together crying, in shock and exhausted...we could hear him in the kitchen slamming about and calling us names. I steeled myself for some man whispering...I went out of the bathroom into the living room to get my cigarettes...he saw me from the kitchen and shouted 'where the fuck are you going?' I looked back at him and then instinctively run across the room away from the door. I felt something hit my calf and looked down behind me to see a knife on the floor...the bastard had thrown a knife at me.
Luckily it only caught my calf and just nicked the skin...I lost my shit...I was so scared but went mental, we argued, he shoved me, at one point me and my friend were fighting with him...I don't remember a great deal after that apart from screaming, crying, man whispering, him softening etc...but I do know my mate slept at my house that night, with his permission of course. She went home the next day. I didn't want her to go but she did. She went on to have a child with him and I know the beatings never stopped despite the way that they always put a united front on when with friends or family. It was like a horrible game.
Many years later another friend asked me if I'd seen the local paper...I checked it out online...he got a hefty prison term for nearly killing another partner.