Question related to dowry and domestic volience

Advice for my sister name Mandeep Kaur got married with Gagandeep Singh in 2012, after a long period around 3.5 years of engagement.She is well educated and working in a college as a lecturer and earning a good amount. My father spent around 40 Lakh on her marriage, many things was on her mother-in-law's demand. Then after marriage her mother-in-law started tourcher her mentally and some time physically. She demanded for a new car. But my sister never told us about all of this. She didnt allow my sister and jiju to go outside together, even to our home. Jiju just visited our home for once. And after one and half year of her marriage they sent my sister to our home for two days but after two days suddenly her mother-in-law came to our home and shouted on my sister and my parents and told them she is not more interested to take my sister with her.She blamed as my sister is not mentally and physically fit. She blamed there is some defect in my sister's eyes and legs. As she visited our home many times before marriage alone and with her full family. Now from May 2013 to till date my sister is at our home. They wanted divorce from us as her mother-in-law wants her son to get married with someone else who has a good property. We went to our local police station but they didnt do any thing and shifted our case to women cell and after 2 or 3 couselling even they didnt help us for anything and they tried to force us for compromise, i thought they took money from my sister mother-in-laws. We file a case for dowry and domestic violence in court but the judge gave us a new date again and again even the judge didnt take the my sister's statement. Before 2 months back my sister's in-laws file a case against us that they gave us 3 lakh cash and my sister took 2500 gm gold from their house when she was leaving as she came with only 2 pair of suits to stay only for 2 days. My sister's husband filed a case of divorce with a big list of blames like she is living with parents etc etc. What should our next step? Should we go to National Commission for women? Will we get the justice for the same?