I am going to talk a little about how we are attracted to each other and will direct you to a series of articles I have written about what is referred to as a General Theory of Love. But the long and the short of it is you were attracted to a whole person. All of her past and evolution to who she has become is part of what you were and are attracted to. In other words, her sexual being was a component of what you are attracted to both consciously and unconsciously.
Her past, as is yours, is what allows you to have chosen each other. Her sexual experimentation was part of that formula. I believe the work is to acknowledge that you fell in love with a whole person and part of that person is a woman who was willing to be sexually adventurous. You have a choice: You can focus on her past as a negative, a deterrent to your future, or you can accept that her experiences were part of what you fell in love with.
My encouragement is to make an appointment with a couples therapist who can guide you through making this shift in thinking. The Find Help tab at the top of the page will help.