Depends on how you want to look at it. Hot Guy (Interesting username lol) has a good point.
However theres things to consider.Like he said don't openly try to drag her away from her "religion".
You could slowly start introducing her to the occult in a way, even if it's through horror movies in a sense, yes they're not exactly realistic (and i'd avoid the exorcist ones and possession ones) but stuff like that always seems to help, it may sound stupid but yeah.
As I said, there's things to consider:How "religious" is she?
Does she go to Church every Sunday? If she goes to church every sunday you've got an uphill battle on your hands brother i'm afraid. Mainly because any progress you make during the week with her to open her up will be immediately undone and thensome when it comes to Sunday.If she's just a christian but doesn't actively go to church then you've got a chance, Alternatively you could leave it a few months and if she really likes you then you can admit to her about your faith in Father Satan and how you were afraid that she wouldn't understand, if she loves you she'll understand, if not then she's just another shallow sheep like the rest of them.
And usually partners are interested in one anothers lives and what makes up that life, so she may be interested in atleast hearing out your faith and you're reasons behind it.
Problem is that Satanism is a faith that each person has to come to and find on their own really, We don't really push our beliefs on others and to find True Satanism in the first place you need to come to Father with an open mind and soul, free of prejudice that is drummed into everyone else.If she can come to Satan with an open mind, then there's a chance.
This is why I go for Goth chicks/any girl that is considered by others to be a bit "weird" because usually their minds are less tainted by christian dogma and they've got the ability to think for themselves instead of being part of the herd
Hail Satan!