How do you stay friends after so much pain?

After one of the saddest stories you will ever hear, my girl of five years left me for a man more able to care for her, and in the same career path as her. I know there’s a lot of hurt and more than enough blame to go around, but I just can’t imagine life without her. I want to move on, but it’s really important to me that we stay friends. Unfortunately, it’s proving difficult to maintain contact and our interactions have been less than amicable. How can I keep her as a loving friend, and not just a bitter memory?