The whole Priscilla surpassing Teresa thing was still just a prediction more than anything, and it didn't have an extreme amount of backing or anything. As was seen, Teresa could've taken her pretty easily from all indication, but the circumstances allowed the eventual result.
I'm not entirely sure that one's continued existence as a Claymore or anything like that indicates how strong they'll be when they awaken. More or less, the way I've interpreted at least, they really can't do much to change the inherent maximum amount of yoki they may have (Hence why somebody like Clare could awaken and dominate other higher-ranked awakened beings with no problem; it wasn't indicative of her skill as a Claymore) and so when Priscilla operates at her max, well, that's pretty much her max.