Otherwise, happiness can be found in any relationship. And if you can make it to the Tree of Life and still be with your partner, guess what.
You will desire to have that eternal marriage, to have that support in taking kids to church, to be able to talk docterine with a like-minded individual. Finally, the decision of whom you marry is really between you and God.
I have known many women who have married non-members and are happy. Should either of you sisters raise your children and wonder what faith will they choose.
Break it off amicably now, before it gets too difficult. Her church is more important to her than you are ever will beplain and simple.