Want divorce

I got married on 15th May 2015 near about 5 months back it was an arranged marriage, just after marriage I realized that I was trapped. Everything that were told about the girl was a lie. She was very anguish in nature, some of her activity suggests that she may be a mental case and it appears to me that the marriage was done against her will. Soon we realized after lot of incidents in such a small span of time that this marriage is not sustainable. She didn't stay more than a month to my home and after that she and her family now giving us threatening and pressurising us from all side to keep her anyhow and carry on with this marriage which is beyond my patience now. Her family is financially very strong and they have lot of political and criminal approach because of a temple in her house. We don't want her to be back in my life and home because she had once tried to commit suicide without any reason and often threatens us to commit. We are a simple middle class family of 3 members me and my father both are in government jobs. My in laws knew about their daughters mentality and they knowingly trapped our family. My wife even abuses me and my family members and slapped my family members as well. Please suggest me legally at this stage what should I do. I don't want her back in my life as it will destroy my life. I am the only son of my family. One more problem is the marriage was local we both lives in Patna that's why they often break into my house and threatens us.