There has to be some sort of foster care or child protective system for this- please read/help?

A friend needs help, and now. She isn't physically abused in any way, I guess you would call it a broken home. At first I thought her drama were just because she was the forgotten middle child, but it really is bad. She doesn't talk to her parents. Her parents can only scream at each other, and for a couple years now shes been telling me that shes the one her family releases all their aggression on. Her older brother is a sports star, and the favorite child. The younger sibling is only a baby, so she's doted on, too. Like I said before, I thought this was just middle child syndrome at first, but everytime she and parents trade words they end up screaming and yelling nasty things at each other. By now, she's given up, she doesn't even yell bad things back at them; just takes it, then goes to her room and lets it out by calling a friend or drawing. But it's been so bad in the past 8 months or so, I'm afraid she's going to do something to herself or run away or try to hurt her family, and that her parents might start raising a hand against her. What happens from here? does the child protection agency have to wait until blows are traded? Becuase this culmination is freaking me out, and this needs to defuse or end or SOMETHING. Please help!