She's blocking him from her thoughts, enough that it's hard to fully establish the context of her comment.

"Healing?" He doesn't really doubt that that's what she means in general, but he's not sure what's throwing her quite so badly. It seems obvious that it would be different in some way from whatever she's done before. He assumes she's never healed someone so attuned to the Dark Side, nor presumably someone she considers an enemy. But it also seems like this goes beyond that. "What was different?"