It's a difficult situation, but I agree the mother definitely needs some help. Maybe suggest babysitting or something. Say, I want to help you help her, but don't step the bounds. I'm a parent so I know how offended I get when people try to discipline my kids without my okay first. My best friend knows she can because I've told her she could, but for other people...if they tried to discipline my babies I'd be bitter.

Get the okay, ask if you can help her...do what you can.