I have to chime in on this one.
My husband and I have explored a poly relationship. We have found someone that makes our lives full.
There are "rules" that we have all laid down.
1. I won't see anyone else.
2. He won't see anyone else.
3. She won't see anyone else!
LOL. Okay, so that may not even be poly, I don't really know but what I do know is that it works for us. I don't want anyone other than the two of them, and they both feel the same way.
I am attracted to both men and women. So is our GF. Our man is only attracted to women. He would never, ever, under no circumstances be okay with either me or her finding another man, or even another woman.
Her and I are both okay with that because we both want this type of relationship. Neither of us want him to share us, except with one another.
So my advice is to find what works for you.
If you can't share her with a man, tell her that. And I don't think that you need to "get over it" either. I think that your feelings are your feelings and you need to share them with your girl so that she knows what you are okay with and what you aren't.
If she came to you and told her that it's not okay for you to do this or that, and that it would hurt her, you would listen and do what you can to make her comfortable right? Exactaly, she will to.