Abusive Marriage

my sister has come out of physical and mental abusive marriage and now wants to start a new life. she was married for 15-16 years and has a teenage daughter.Her daughter has also accompanied her and now both are living with me. it was an arranged marriage but things were not right from the first day. Her husband had illicit relationships with bar girls which was known to his parents as well matters became worse as he started hitting her regularly in drunk state. He is a daily drinker,smoker,gutka consumer and jobless. She had left him and came on 4-5 occassions previously but family and parents intervention pacified and send her back. This time it for good and on realising that she is not intending coming back this time her in laws have said that they will not compensate or give divorse. What are our options