1. She was either with someone before marriage
2. or she was never interested in getting married or married to you, just did it coz her parents forced her.
You dont have much options.
One as some LD members said, talk to her parents, hold a GD talk it out, see what comes out, ask her parents to tell her to modify her behavior and to lead happy marital life.
If at one point if she agrees that she was with someone, you can ask her to forget the past and move on with life with you.
If marriage is not consumated, then if she is very adamant of changing herself, then better part ways via MCD.