Daughter in law with her 3 years daughter

I would like to register a complain against my sister in law (Bhabhi) on a serious note. My mother is about 61 years old ailing lady and is not able to walk properly, she very week and facing mental torture from her daughter in law. She is lawfully owner and having physical possession of property bearing H. No. 657, E-1, Ground floor, Gali no 11, Nehru Vihar, Delhi -11094. Area of about 100 sq. Yards. She resides with my old father suffering from diabetes. Our family were four member in total. My brother was married in April 2015. But coincidentally he got expired in a long treatment in All India Medical Hospital on 26.10.2018. After his death on the instigation of her family my sister in law threatened and misbehaved with my old ill mother and father. Forcing them to transfer all the property on her name otherwise she will commit suicide and will falsely implicated to all member including me my husband. She has tried four attempts for suicide in the recent past whose record are with near police station Gokul Puri. But police in charge is not taking any action and ignoring them. She consumed slipping pills, on 05.07.2019 evening 16th July and 30th August on record. In which at Two incident my mother called the police by dailing 100 number. Police admitted her to GTB hospital. She even has given this statement that she wants full property. But no body has taken action against her. Due to which me my family and my mother and father lives in fear. Recently she said that she will file false case against my father for assaulting her. Because of which my father leaves his house don't want to return and in mental trauma kind situation. My mother has served a notice in Rashtirya Sahara daily Hindi news paper for misbehaving and to protect her self. Also she sent a legal notice to daughter in law. But she unable register a complain in senior citizen cell. Please help her.