What should my sister do?

My sister got married to a software engineer in 2002 and now they have two daughters. They reside in US. My sister is also a software engineer, but she is not happy in her life as she is been emotionally tortured by my brother in law. My brother in law expects financial help from my father, but my father is not ready to help because he is totally against the marriage of my sister. Her's was a love come arranged marriage. She is suffering a lot and dont want to take divorce too because she thinks her kids will suffer in the future without a father. She is simply undergoing the mental torture given by her husband. She is going into dipression day by day. I am very much concerned and worried about my sister. I am her brother and i am not in a position to help her because she lives in US. I cant give any financial support because I work for a small organisation in Bangalore. Sir/Madam before the situation becomes too worse, what is that I can do legally from my end? Please help me with your valuable suggestions.