Did you ask her or did she volunteer the information? If she told you out of the blue, I don't think that was an appropriate and decent thing to do. It's like rubbing salt on your wounds.

If this is the case, "forget about her!" When I find myself in situations like that, I create my own little rituals around the problem. I might write a letter about how I feel, find a photo, put them in a steel container and burn it. As it burns visualize yourself getting rid of her negative energy and allowing yourself to be cleansed from all things hers so you can be open and pure for tour next relationship.

Good luck!