Proceedings in India after one sided divorce in US

My sister got married in India only while she was working and staying in U.S. Even her husband was there since very long. This was an arranged marriage fixed by the parents ( both staying in India) . Due to her husband's odd behaviour and thinking my sister started going in depression over there. Even her mother-in-law would keep calling and abusing her on phone. After some research I did on odd behaviour of her husband I got to know he has "paranoid personality disorder" which is incurable. Also they pressurised her to put her money in buying a house over there wid equal contribution from both. After 5 years of marriage she decided to divorce him. But before she could react her in-laws reached there without any prior information to her but husband knew it well. Now they have filed for divorce and were making her life hell when my parents had to intervene and had to reach there in a short period of time. Now they have decided to oppose fighting divorce case in U.S. by filing an application " under Hindu marriage act". They want to fight d case here in India. My question is 1. How she can go about d case in India while staying and working there. For her just coming once to file d case in India wil b enough? After that my father can do d needful. 2. About streedhan , her mother- in-law is refusing to part wid it while lying that it has been returned? What action she can take against her? 3. We want to file divorce case here on d grounds of " unsound mind " of her husband , how to prove it and go about it? Can she claim compensation ? If yes how much ? His parents have got 2 houses here and they r planning to take over that house in U.S. too. Her husband works on contract basis as he cannot sustain in a job for very long due to his strange behaviour though he manages to earn well.