Board Thread:Questions and Answers/@comment-29781768-20170925090542/@comment-84.100.51.27-20171009173343

There's also the fact that Priscilla predicted where Subaru would go in arc 3 and that he would want to enter the castle (she even told Al what Subaru would say), you can check the manga. She might have a gospel.

I also remember someone on 4chan saying Emilia instinctively disliked her as soon as she saw her, which would make sense given her past with Pandora, but I don't remember the source.

Imo she's definitely linked to Pandora. This having been said, I think it's more likely that she's just Pandora's pawn and not Pandora herself. If Priscilla is supposed to be her cover then she's making it way too obvious given the way she acts, though you could argue that's not a big deal because the only character on Subaru's side who knows about her is Emilia and she'd be too dumb to figure that out. On the other hand if Pandora is indeed the main villain it'd be weird to have her show up only in flashbacks until very late in the story, so having her disguised as Priscilla would make sense.