I somehow have the impression that SH is actually not a true follower of Shar. She said she has memory loss, and also had some strange magic occurance. I think she might be something else originally, and her chains that made her a Shar follower are breaking - just like Astarion can walk in daylight now thanks to tadpole buddy. Maybe the magic display was her true powers showing. Hells, she could be an abducted, brainwashed Selune cleric. Now, that, would be an interesting plot.
