Divorce

My brother got married to an advocate 1 yr back. just after 1 week she started mentally harassing in the name of law as we didn't know anything about law we kept quit. after some days if my mom or brother argue with her she always used to tell them that she will file the case against us. after 6 months when brother couldnot control because of her torture and he told her mother that he will give divorce but her mother promised she will not do again and she came to home back apologized for her behaviour and promised she will not repeat the same. after 3-4 months again she started the same and it was above our limit that she started beating my mom and catches her neck and next day after returning from work suddenly she started shouting and called our neighbours that my mom and brother are beating her but our neighbour know us very well and at the same time my mom was not in home our neighbor scolded her and my brother was afaraid she will do anything herself so he took her to her mom's place. after 2-3 days she alone early in the morning came to home and she started beating him and as my brother thought in that time if he reacts if he beat her she will register case so he ignored. and he informed her family that he going to file the case but her family requested not to do so. ther family came to our home when they came to know all the thing which her daughter did they apologized even she has apologized and told us that she will not repeat and request us to give one chance . we agreed as my thought not to spoil one girl's life. within one month again she started the same behavior and she tried to suicide when my brother saw her he called my mom and sister for help. my mom and sister went and removed her and slapped her for her behavior and asked her y she is playing with her life. she argued a lot and after half an hour she packed her bag and left our home. on the next day she came with her family and she accused us that we tried to kill her but this is not true. now this is over our limit and we can't bear we brother planned to divorce. please give us advice for the procedure. They married as per christian law. and i told them to register ther marriage in civil court and after several time tell her she didn't register marriage in civil court. kindly note when she asked us to give last chance we asked her to give apology letter so at least for this thing she will change and at that time she asked apology to all our neighbor start she told lie. and we can't understant of her sudden change in her behaviour. ( Please help as we don't know about law)