Harassment by husband and mother-in-law

Hi, My sister got married in 2013. Her husband is working in a professional software company. After three months, she came to know that he is a psycho and not a self-thinking person as he will always hear his mother wordings and started to torture, threaten and beat. His family has ill-treated my sister with offensive language and totally abused her to the core. One day, he also slapped my sister heavily and her ear drum got damaged. Then I bought her to my home and took a treatment for ear damage. After two months, I took my sister and left her in his home and advised him to lead a happy life with her hereafter. Later, he started to abuse her physically, mentally, emotionally for not getting pregnant. She also went to doctor and they told that there is no problem in conceiving and gave some treatment. In mean time, he got an onsite opportunity in USA. He and his mother planned to leave my sister in my home with the name of treatment and not to share any information regarding his travel to US. Without knowing their, my sister also underwent for an IUI treatment and got conceived. By that time, the travel ban issue on H1B visa was announced. So he could not move to US and totally annoyed putting the full blame on my sister. She got much dispersed and the baby was aborted. At last, she is not interested in leaving with him and came out. Then, I went to his home asked him about my sister life, but he is not interested in speaking with me and sent me out. Now, six months passed away and no conservation or interaction between my sister and him. Till now, I did not take any action against him and his mother. Please advise how to go about.