Dowery and torture

My sister is married to an NRI in Australia from past 5yrs and staying alone with her husband and her 3yrs old kid who is born there only. Her Husband's family is staying in Delhi. Before shifting to Australia, she spends 6 months with her in-laws in Delhi and just after a month her in-laws got very demanding. They took all her jewelry and asked for more money.Every middle class family want to see her daughter happily married, so at that time we fulfill there demands for the sake of help. Before leaving to Australia they argued with us and ask for more money because of that issue my Dad got heart attack and he is no more now in this world. Now the main concern is her husband is not filing PR of my sister as she suppose to get after 2yrs when she shifted to Australia also torturing her to not to go out or talk to anyone and hitting her as well. My Sister said sometimes that she will commit suicide because things are getting over and every single person will loose their patience one day. Please help us how can we put case on her in-laws and husband, so that we got our all our money, jewelry and justice for my sister. Please help..