What do you do when you find out that the person you love have betrayed your trust?
You forgive them and try to move on. That's what you do. It's no use hating them, because it takes a lot to hate someone. The best thing you can do is to forgive them, pick up what's left of the relationship and try to make the best of it. Many things will change, you may never be able to go back to what you used to be, but that's just life for you.