not sure who to ask for help

My best friend has 3 kids ages 9 to 13. She also has a live in boyfriend that has 2 kids (ages 6 and 10) . She has always been a giving "yes man" but I've watched her this last year becoming more and more tired. Angrier and more hostile. Between the 5 children there are 3 dad's. They are for the most part shitty men. Especially the dad of the oldest 2. Anyhow. They either tell there children. They don't have to listen to there mom and they don't have to follow her punishments. Or one dad just spoils the child horrible. So I was there one night to do crafts with girls. In 3 hours 1 child broke another's brand new toy. One child "stabbed" the mom (my bff) with a knife with the sheath on. And another one said loudly she would much rather be at her dad's. She hates it at her mom's house. by the end of my visit my friend grabbed one of the kids by the arms (rather hard) and kind of shook her while saying does that feel good to u. I've never seen her like that. Lately she had been cussing and yelling so much more but this was extreme. So I told her 2 days later I was worried. I was scared for the kids and worried she was going to actually hurt the kids someday. She started yelling and crying and telling me her kids are aweful people and because of the dad's they all run over her and mentally abuse her. All kids and her are in therapy but not seeming to help. But she admits she gets so angry she has to walk away but sometimes her anger gets out of hand not sure who or how to help her. But I love her and she does need help. Any ideas?