I just realized something, I think the injuries Priscilla received from Isley at the start of their fight DID give Priscilla amnesia. She had her typical "dream-state" personality until after Isley injured her, and then all of a sudden she starts throwing out a huge amount of energy and her personality changes.
My guess is that Priscilla was somehow holding her power back subconciously (similiar to how she spares little girls subconciously), but her amnesia somehow unblocked that power-check.
Something that just randomely crossed my mind as I was re-reading the extra chapters today.