I'm also in favor of the guy and the girl having "their time and their space" with their friends. Guys need to get away from time to time with their buddies, and the same applies for the girl. If you don't have this balance, I don't think it's healthy for either in the relationship.
My wife and I have been together for 12 years and married 10... I get plenty of opportunities to have "MHM time" with my buddies, and she gets those same opportunities.
I also don't have a problem with my wife going out with her single pals to a bar, it rarely happens, but I trust her and she's never given me a reason to question her. And, the same goes for me...
Looking at your situation (based on little information) - if the trust isn't there now, I doubt it ever will be.
Question - how old are the two of you, based on the situation I would guess young (early or mid 20s). Some people are ready for deep relationships at that time in their lives, but many are not.
I'm also not as big of a fan as I used to be about the "moving in together" idea before you're married. For the sake of this discussion not taking a different path, let's leave the 'religious aspect' alone... but, moving in with your girlfriend just doesn't work out the majority of the time. Sure, some will say "it will let us know if we're supposed to be together and get us ready for marriage". It's possible, but it doesn't sound like either of you is mentally prepared to deal with it... especially the girl.
Look out your window... she's not the only available girl out there, and based on the issue at hand... she's likely figured out that you're not the only available guy.
Don't be the victim, man up and confront the situation directly... stay positive and rational, but if you let it drag on... there's nothing but pain in your future.