This is irrelevant to the love spell, it has nothing to do whether someone knows you're a Satanist or not. Though if she's still a xian and she still thinks that Satanism is bad the spell will probably have negative effects. I mean, it's possible for her to love you so much that she will be obsessed with deconverting you. Xian girls of this type are the worst, you can't get rid of them even if you break up with them. They'll keep pestering you.