what would you do?

My sister moved with my mother in law three years ago and has no contact with my family. She is 26, and rejected all of our call and then changed her phone number. My mother cried because she miss her daughter, and both had not argued about anything before she left. My mother in law manipulated my sister in telling bad stuffs about my family and she ended being traumatic when she was near us, so she ended living with my mother in law because she offer my sister a room to move with her. It's been three years and no contact from my family. Sometimes I go with my husband to visit his mom and I see my sister but she doesn't talk to me and act like she doesn't know me. Is there a way that could do to have her back? Like file something or there's nothin that can do? Any advices or someone has similar stories but different.