I have a really awful visceral reaction to her, which is totally my own issues cropping up- memories of my mom acting like that..memories of myself probably seeming like that.
Don't be too fast to accept blame here. Your visceral reaction I think is pretty normal describing what you are seeing....plus, you are a mother yourself...
I don't even have kids, and my guts are retching reading this...
I agree with Dandy, you can call CPS. MY GOD if you ever see her drive those kids, please call the police.
Also - take care of yourself, that would be really, really difficult to watch.