How sick does a person have to be to equate having a long-term close friendship with a member of the opposite sex to a perverted non-Christian lifestyle?
I'd fire the question back at you, and ask how deluded you have to be to believe that a relationship that was "romantic at times" didn't include sex. But I won't ask it, because we both know you don't have any such delusion. That's why your starting point was that "her love life is her own business." Unfortunately, you can't have it both ways: if she's such a devout Christian, and we're supposed to believe she will ajudicate accordingly, then her position on, oh, sexual purity, becomes relevant.