How do I ask my male best friend to hang out without his girl friend?

So over the past year my best friend has been attending a school in another state and here he met his current girlfriend. She is a very cool girl and I have no problems with her. The thing is they had an issue with their school so they had to essentially drop out (with good reason). But because of certain issues he moved back and she came with him. This means they currently live together which also means she is ALWAYS with him. So at every group hangout as well as what is supposed to be one on one she is there. This can sometimes be uncomfortable because I never want her to feel excluded and it is very hard to carry a conversation without inside jokes on past memories being brought up. Everyones knows its always uncomfortable being the person who isn't close to a group so I never want her to feel that way. This sometimes can take the fun out of things because of worrying for someone else. But also even when I call to yap and let out my private thoughts she is always there listening. This is something I do not like because I am a very private person so it takes a while for me to open up to someone to truly get to know me and she also comments on what I am speaking of. For example my pet bird died and I was a wreck so he called me and I was sobbing and super upset and I heard her speak in the background obviously listening in which really put me off. The thing is I am a girl and I never want to be seen as the girl best friend who comes between a relationship, but I would just like to hang out with my best friend one on one in a place where I can truly speak my mind and not have to worry about someone else or what they think of me. I do not mind hanging with her but sometimes I wish it was just us. I also really want her to like me so I don't want to get on her bad side.

How do I ask my male best friend to hang out without his girl friend?
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