My sister in law physically attacked my father and mother

I am their daughter and live in different city. My sister in law lives with my parents in Varanasi and my brother Lives in different city. My brother has filed a divorce case in August 2019 due to her adultary behavior( we have case against her for adultary) and misbehaviour with him and my parents. After filling divorce case she filed many cases against them like dowry, dv, rape to torture them. We also filed cases against her for her ill behaviour but police never helped us and never threatened her for her act. They said she is women we can't do anything to her. You live with her and give her what is required for her. We did the same because even after complaints we were feeling helpless. She always threatened my parents saying she will kill both of them and my brother or will ask someone for the same. My parents are of 65 years old citizen, very simple and respected people. They get scared with her threat and tried to record her threat but living with her somehow. One day she called 5 people in our home around 8.30pm and beaten my parents near death. They got injured very badly. They went to police station and got medical report. With the help of God my mother has kept her mobile on recording mode when they were beating them with danda and abusing words. We have also the video recording when those people came and left in our areas CCTV. We have reported everything to police but no action has been taken to protect us. We also contacted dig for our protection. We don't know what we should do now. We are feeling so helpless right now. my brother is very much scared for his life and our parents. Pls suggest your valued suggestions, we really need it.