My grandmother’s mental abuse by her daughter in law.

My grandmother, 75 year old resident of Nashik was a teacher by profession. She has two kids. She lost her husband very early in her life. Since then she use to stay with her parents and two kids. During her job, she achieved many things in her life and build her own house. Currently she stays with her own mother who is 92, her son and her daughter in law. I’m her daughter’s daughter. My uncle got married around 13 years back to a woman from Nashik. An arranged Marriage. Post their Marriage, around 7/8 months later she started the mental abuse with both my grandmother’s. She has made strict rules at home where no one is allowed to enter the kitchen and disturb the setup. They are confined to their bedroom. There’s no sense of freedom in their own house for them. She even asks my grandmother to wash dishes at this age. She doesn’t make their food at home. Their food comes from outside through a tiffin service. They are helpless. I need advice on how I can use law to shake her.