Just be prepared she might break up with you if you bring up such a subject.
Come to think of it, it might be a good question to ask if you are trying to break up with her.
It's a win win for you. If she breaks up with you, you've got what you wanted in the first place. If she's game to have a threesome or orgy, you still win right except that you'll have to find another time to up with ..