Dowry harrasemnt

My sister was married for 6 months ,her Inlaws possed a rule that she should not talk to us (mother father )on the day of marriage because we had disputes on the day of marriage on pending dowry settlements. We thought time will heal it and my syster started reporting their verbal harrasemnt for last few months.. they used our dowry money to use for a down payment of their house in bangalore . And we were aware this but thought it's our sister life hopefully she will be happy .. After 6 months she called one day and said she want to come to home as her inlaws were giving verbal and harrasemnt ; it gone to a stage that her husband started hitting her and her father Inlaw also started to hit her ... our heart was broken in to pieces after hearing this.., my sister is in my house and I want to take this leagally A) every month they take all her salary B) they used our money for down payment of their house C) it's very heartbreaking to hear that her father Inlaw is commenting about her dress D) it has now gone to the stage of father and son started hitting a pregnant lady , so we decided to respond legally We have our sister in our house Her in law as are in Bangalore and wedding is registered in bangalore , we are in chennai how do we proceed with this Pls suggest