This happened to me, only much younger. I think I was six the first time my mother told me she wanted to leave my father but that if she did he said he would kill us. I think last summer was the last time she said the same thing to me.
And it was like once she’d started confiding in me about my dad, she just kept crossing deeper and deeper boundaries. and of course, I WAS NOT TO TELL ANYBODY.
I don’t know if she ever even had to tell me that. Geez.
I think it happens with abused women (or maybe more back then?) and their kids more often because there is no one else to talk to about it. Because GOD. The NEIGHBORS can’t find out! They CAN’T know at WORK!
It’s embarrassing. And the kid has already seen most of it.
I’m not suggesting this was in any way your mother’s motivation, but I think it had a lot to do with mine.