Damn it bob...you sounded so happy in that other thread where you posted pics of the two of you. Sorry to hear about your troubles here.
Anyways...I don't know where some of these guys get off implying you're in this just for sex, it seemed pretty obvious with the other thread and all that wasn't the case. Remember that a good quarter of the guys who reply to these threads are the ones who've never touched a girl in their lives, or have been left in the dust by girl after girl, and reply accordingly.
My own bent is pretty anti-religion so take that into consideration when I ask why she's brought this up now - is it because things are getting that serious? People don't tend to have attacks of concience (sp) out of the blue like this. Are they responding to something their mother/father did? Even more ugly a question, are you sure she's happy with everything up to this point? She does owe you some answers, but get them from her gently.
In any and all cases, fight for her if you care about her as much as I figure...don't give up easily or go "re-evaluate" like some of the snivelling wusses here have said because it's *your* fault somehow. Maybe the simple fact is she doesn't know how much you care and isn't willing to break ground with her faith because she has no commitment from you. Questions, questions, questions. Take tonight and clear your head and go find some answers. Good luck man.