Mel, when you rearrange the rock, you might want to keep a bit more in the upper tank, so the new tang has places to hide till Priscilla calms a bit... If you leave it too open for space, its more room for her to terrorize her in as well... I know my Christmas wrasse was scarcely seen for a few days and really appreciated the rock cover when I threw my Sixline wrasse in there with her... They get along dandy now... But the rock provided a good buffer for the time being... Hmmm, perhaps you might consider some sort of wrasse...
Also, a cleaner shrimp would be nice for Priscilla as well as your Powder brown... Oh, and I LOVE my ASM G4 plus skimmer... My hair algae is disappearing since I added it...