I agree with bombmaniac that she should disconnect emotionally, HOWEVER its nearly impossible living within close proximity to the mother never mind IN The same house! THerefore, it is my expert opinion that everyone who has to escape abuse and rebuild their life should be physically distanced from the abuser.
She must and should get out of her mothers house. She can find someone else to live with. AS long as she remains in there she will be a vunerable victim just as she has been her whole life.
She must start a new beginning.
FIrst thing that she is responsible to do though would be to recognize the gravity and severity of the effects of the abuse and emotional debilitation its causing her. Then when she realizes something must change, she should reach out to an older mentor who can help her find a solution. The ONLY solution is to move out. Move to another house to live in.