i believe you are saying she is a staunch christain...well, i
can only say, either you convert, or break up. simple. By the way,
non-christain can also hold a church wedding k...depends on $$$,
and of course certain chapels need you to be christains. all
depends one..
hardcore christains will do anything within the bibble..believe
me..if you dont see yourself as one, i pray hard for you.. leave
her. Indeed she had sin when having sex with you, but in reality,
both are willing. Since you are non-believable of the cross, you do
not need to worry about the sin.
As for her, if she force you to become christian out of your own
will, she double sin 
. And if she continue
to stick with you as a non-christian, she also sin
. And worse, if she
continues to have pre-martial sex with you, also sin
.....SO,
LEAVE HER NOW...unless both of you can really compromise, i will
surely give you 2 the blessings... 
