Domestic Abuse

My sister is facing few problems. and she has tried to commit suicide. Problems like her husband is verbally abusive,controlling everything(money she earned, food she eats, etc ) and not sure if its physical abuse also. Her mother in law Demands stuff and money indirectly a lot of times, ill treats her, very verbally abusive, physically keeps pinching her hard, makes her sit and sleep on the floor. In the name of customs this is done. and when my sister was gifted with a baby girl , she blamed it on her and verbally abused and pinching on the hospital bed after a c section. ( she(MIL) wanted a boy ) . The whole family is very money minded. But everyone is really good at showing off to the world that they are good. like now they have accepted the girl child got her expensive ornaments. And apparently all the problem is created by my sister and she is the problem. She is really educated (Btech + MBA top tier college ) (Even my BIL is from top tire college ) but she is really innocent and wants to see the good . they are playing around, the situation is really bad. Now blackmailing her with various things.Now hee wants her to bend to all that his mother tells to do and follow (uneducated people, and science dosnt make sense for them at any cost ) she is now telling her to do things to the kid which the doctor has told not to do as its a danger and warned about few dumb customs(which science deneies ) of india. and if she dosnt lot of conseqences My parents gave around 8 lakhs cash(to bank account) and property worth over 1 crore to my sister and a lot of gold ( they just love gold :/), which i tried to explain to my parent in the start that greediness doesn't end, which no one heard. i got few voice recordings which were deleted by her husband from her phone. now nothing is there now. me ,my parents and few relative a have witnessed few things. I want to know what precautions i can tell her to take and whats proof needed to nail all this people. I just want to make it fool proof. Everything is upside down here. Would love some help. would be very greatful. I want my sisters and her childs future safe. PS : 1. the father in law was in the police. 2. My BIL might get a doubt about anything i do to get proof, he is really smart.Please Help ? I feel this is dowry harassment,girl child , what else can it come under and what to do Abbreviations used : MIL- Mother in law,BIL-Brother in law, FIL-Father in law