If religion is important to either of you, then perhaps you shouldn't get too serious.
When you are young is the time to meet and have friendships with all kinds of people and learn as many happy and painful lessons that need to be learned in order for you to become a knowledgeable and well-balanced adult. I can see by your question that how folks choose their religions is confusing to you, religion is a very confusing issue for young people(and adults, too).
You just have to live and learn, and seek advice from a stable adult whenever you are dealing with difficult issues.
Good Luck on Life's Journey