Suma - This is a pro-marriage site. When I or someone says run we are not suggesting get a divorce. Or at least im not. I fought for 2 years for my marriage. What im suggesting is YOU need to take a serious look at your life and R and decide if you have what it takes to be with someone like this.
Anyway you spin it she has already betrayed your trust. You cant put your head in the sand about this. She needs to prove to you that she is worthy of your love. Not the other way around.
What I suggest is making a list of Boundaries and Consequences.
I would tell her that you are having serious issues with trusting her and that you need time to figure things out. I would tell her that in order for you to have any kind of future you both need to go to counseling to work on your self-esteem and communication skills.
If she is serious about your future together then she will agree if not then you have your answer. Once again. Some people were never taught what true COMMITMENT and HARD WORK is all about.