Torched by in-laws

I am seeking advice related to domestic violence in the family for my sister. It's been above 13 months of her marriage and just after few days of her marriage her MIL started taunting her for her appearance, dowery, her family etc. She never agrued with her because she was told before marriage that her MIL is very aggressive kind of person so to avoid any conflicts try to avoid her. But day by day situation got worse and dispite of her husband's support to her, the environment of the family got very bad just because of one lady. All together they are 4 people living in the house. FIL,MIL, my sister and her husband. One day her MIL started abusing her and used foul languages for our family. My sister thrn said to her not to say anything to our family in loud voice. Her MIL just lost her temper and step forward to hit my sister. Luckily her husband protected her and asked his mother about all the drama. Her mother said to take my sister and leave alone. My sister never wanted to leave her house because she has the right to leave there. Though after many discussions conclusion came out to leave saperately in one house on another floor. All the problem of her inlaws was that she did not know how to cook though she told this to them before Marriage only. And after she got married she was trying to learn cooking also. But inlaws seeing her one weaknesses started humiliating her. Mentally she was getting weak day by day and to protect her, and for home peace her husband got all the things for themselves in another floor. But things still are not normal. Now my sister has got a baby who is few months old and now inspite of living on another floor after every 3-4 days her husband's mother creates one or the other drama and forces them to leave the house and still abuses my sister with very bad words. She cant go out or work to avoid all these day by day intense torched life because she has a small baby. Inlaws don't give car keys to the husband when they need to go somewhere. Still she get to listen abusive words for herself and her family. She wants to file complaints for her inlaws as now things have got very bad and she and her husband from his parents gets threats to leave the house. Her husband is the only son and they have got one more daughter who is already married. My sister wants to know this also that is her baby or her husband or she herself any right on property. House is made by her FIL himself. And she also wants to take corrective action for her MIL as mentally she is torching her. Please let us know what we can do.