Three Way and Have a GF, how does it work out

I have been together with my gf for a few years now and we have gotten very trustworthy of eachother and very open with things we'd like to do. We get into threesomes one night and she asks me if i would want two girls and I say of course. I ask her if she would like two guys which since I love her and completely trust her, I would be ok with, its just sex right, especially since she thinks she would give me another girl in bed. She says shes not sure, she thinks she would be more comfortable with another girl in bed [img]/images/graemlins/grin.gif[/img], as she thinks she would be uncomfortable with two guys inside her. We also come up with how bout if it was another couple, I say yeah I think that would be ok and she thinks thats what she would prefer that the most. So here are my questions OOT. And any thoughts on the subject apreciated.