Hi,
There is no future in your relationship with her. She cheated her husband several times, cheated on you already, what makes you think she won't do it over and over again after you married her?
Do you know why you got involved with her inspite of all this mess? You believe that you are saving a damsel in distress. That way you will feel better about yourself. My friend, don't believe that you will feel good by being with her, she will just make your life very miserable.
So just e-mail her and tell her that you have changed your mind and ask her not to contact you ever again, change your e-mail address, change you phone numbers. This is going to be tough at first but eventually you will forget her.
Find a nice lady who does not play games , someone who will deserve your goodness.
And lastly, don't ever give anyone a chance of putting a big sign on your forehead saying '' I AM STUPID AND DESPERATE ".
Take care and BE SMARTER NEXT TIME.