This can be very difficult. But in the end, it all comes down to what kind of beliefs her religion really has. If she really, truely believes that your lack of belief will ultimately result in your going to some form of hell, then she’ll probably start trying to convert you at some point, which could put strain on the relationship. If her beliefs don’t fall that way, the relationship may go strong for years to come.
The most important factor here, as with all relationships, is communication. Communicate your concerns and start an ongoing dialogue with her on how your differences in religious view might impact your future together. Keep yourselves on the same page, keeping each other’s feelings in mind as you continue. Just as you might not want her trying to convert you, she may have concerns about you trying to de-convert her. Be honest with each other and don’t let your fears keep either of you from enjoying your relationship.