I agree with Hannah. Make sure that neither of you are drinking at the time of your "talk" and also, maybe show a little bit more PDA. She could be flirting to get your attention. Hold her hand, kiss her cheek you know little things. You don't have to shove your tongue down her throat but gently show other people that she is with you. ;-)
The best thing to do would be to talk to her and tell her that you are not comfortable with how she behaves around your guy friends. You should also avoid instances where you spend too much time with her around your friends and make it a once in a while occurrence.
She probably wants to make sure that they accept her as a friend So they don't try to break you two up by telling you lies and spreading rumors. Plus there has to be trust for a relationship to last. Don't you trust each other? Peace
This is an if answer, if she's flirty with them she may just have a really friendly personality, if she's flirting with them like she flirts with you then she needs to know gfs don't do that, either way, though, talk it over with her, a little communication helps relationships grow in the right direction, if she gets mad at you for bringing it up, then she may not be the gf for you.
Well, darlin', you have a flirt on your hands. This gal apparently needs more attention than any one person can give her. She is validating herself through these flirtations. She sounds very insecure. Accept it or move on. You can't change gals like that.