I'd say that you need to try to get over her prefect. I'm very sorry, but sometimes this happens. If she had wanted to just open the relationship, and see both of you, then I could understand.
Just because your relationship has changed doesn't necissarily mean that you can't stay friends with the same people. If she intends on this to be friendly, and you want to keep things a bit cooler, then try to act relatively normal. You can still hang out if it doesn't hurt too much, and you can still see the same group of people.
Best of luck Prefect. If you ever need anything, you know that we'll all try our best to help.
