I honestly hope she is evil and she's only nice because she's messing with you. THAT would be so freaking cool and I'd actually respect her as a character more if she was actually, genuinely a Sharran priestess who was putting on an act the entire time.
All too often, "evil" simply means "Wears black and has a sardonic attitude." Is it any wonder that "But are they
truly evil?" is a common refrain these days?