I've been dating a girl for about 6 years now- despite that, I still go out a lot with my friends, go to parties etc. , sometimes with my gfm sometimes without her.

I find that when i'm with her, other girls are polite to me but give me very little attention. They will end up talking to my gf while I hang out with the guys. If I go somewhere without her though, even in the same friend group, the same girls will be way more receptive to talking with me, joking around, play flirting. This has seemed to hold true across many situations. Is this normal behavior?