Regarding petation of divorce

My cousin get married in 2012 and her in-laws are not treated her well.Her husband beat her,abused her,dont give her time and also he don't have money for her.Her in-laws once proved her mentally disorder and saying that she is not well and tell us to take her to a doctor,after that we consult to doctor and the doctor checked her and she had a full body checkup and after that the doctor told that she is ok,she don't have any problem and she is week and slim because she is taking to much tensions.We showed her in-laws all the reports and tell them what's the main reason behind her weakness,but still their behaviour was same,so we took step and we take her away in thinking of that the things get normal but the things get complicated what we don't expected.She had to suffer a lot but she don't take any action against that.She just trying to settle all these things.From few months she was with her in-laws.,and her husband don't even talk to her and before 10-15 days she and her husband live separately from her in-laws as per her husband wish and he told her to be at her home place for few days because he had to go for a trip and when my sister is at her home and she get a petition for divorce.For further please contact me. I kindly request you to please suggest me some way out of this.Its about my sister life.Can I file a case or what!!Please give your advice.