Help with a sad situation...

My daughters friend is 16, she lives with her abusive mother (most recent she choked her, spit in her face & called her racial names) & she’s dating a 24yr old man (her mom approves) & he’s also physically & emotionally abusive with her. 2day we hid her, because he choked her, pulled her hair & actually bit her… Needless 2 say I had 2 take her home to get clothes & her mom made her stay there with the boyfriend!! I’ve been trying to help this girl since she was 12 or 13.. My heart is breaking 4 her. The sad thing is that she don’t have anyone else to turn to…(no father or extended family) & her mother won’t let her move into my home because she doesn’t want to give up the benefits she gets from the government!!! (oh I 4got to mention that mom is addicted to crack cocaine) I’ve told her mom several times to keep her benefits, my only concern is the child. Everytime I see her I notice her spirit is more broken. I’ve called the local c.p.s. About the situation & they did nothing. It’s sad.. She has a younger sister that gets treated like a queen, I can’t figure it out!! what do I do 4 her? My next step is a lawyer, I don’t know what else to do!!!