My girlfriend father is abusive and beats her wife and daughter

My girlfriend father have been physically and verbally abusive towards her daughter and wife from very long time, yesterday on account of my girlfriend asking her father to stop eating tabacco, he beat her until she lost consciousness and kicked her in stomach. And then called police on her complaining that's she's mentally I'll and and need to be institutionalised immediately, once my girlfriend told the two police officer what happened and what he have done to her they only told her father to don't do it again and left, after that her father threatened to chop her in pieces and throw her. She have tried many times to convince her mother to file for divorce or do police complaint but she denies it being afraid of the backlash froms family and society and who'll earn to support the family. My girlfriend been a cancer patient and have lost ability to use her hand and is unable to defend herself, she have eye witnesses of the incident. Iam very concerned about her and have no idea what to do.