Great post and good question.
It's possible to both maintain your own religious views and have a great relationship.
The key is MUTUAL respect for the other's religious belief.
I suspect you're willing to accept her Christian faith right?
Sooooo.....It all comes down to her willingness to accept you , as is.
Sadly, most people feel a strong need to convert others to their belief.
You're right, and it sounds all dandy, but the kicker will be when they have children, if they do remain together.
Women have a tendency of getting very moral and possessive once there are children in the picture and depending of the indoctrination She had by her parents, you're almost guaranteed she'll transmit it to them, whether you like it or not and that's when the shit will hit the pot! She will use your children to make you feel guilty of your "moral irresponsibility" and the in laws stick their nose and brainwash her even more, You'll be the Bad Guy every time!
Unfortunately, in most situations like this, the guy is in the losing end, and winds throwing the towel and leaving.
Once indoctrination about any religion is embedded in any individual, it's there for life, just look at them moozzies and their fucked up beliefs, it's a bad seed that has been implanted from very early on, and it will stay with them till the end of their pathetic brainwashed lives....