Is quick divorce possible if the girl wants to marry someone else?

The girl and I love each other for the past 4-5 years. But due to family pressure she had to marry someone else 4 years ago. We kept quite at that time due to fear, but now it's too much. The girl belongs to a muslim family and I am from a Hindu family. She has no kids. We fear if we directly talk to the family members or the boy, who she was married to, we may have a threat to life. So getting a divorce in that way seems a little risky. What can we do? Should we both go to the police? Or should we get married in the court and then go to the police? Is this even legal or possible to get married in the court if she is already married? And in such case, does the girl have to live with them (we fear for her life), until the divorce is complete and if so how long would this take?