That is the problem with being young, you are always so unsure
about everthing.
Why date? Why get to know each other better? Might as well
everybody simply pick each other out in a parade and go straight to
the ROM.
The whole point of dating is to find out about these types of
problems. Now that you know there is this problem, then get out
fast.
It is only 3 months and you have so much problem breaking up with
her.
Tell her that you do not mind her being a Christian and if she
respect your personal beliefs, then the two of you can continue. If
not, you have to break up.
If you tell her that you do not mind; then what that means is that,
you do not mind her going to church and leaving you alone... or
worse, she insist that you go with her.
If you tell her that you do not mind; then what that means is that,
she will want your children to go to church with her... or worse,
your children end up wondering why daddy is "like that one?"
So my advice to you is to find a girl who has the same mind as you
in important matters.