Charlie manages with the backlash of the sudden movement better than most would, which Castiel finds interesting, but chooses not to comment on.

He nods in response to her. She shouldn't be searching long. Those two Winchesters aren't exactly hard to miss, generally. Dean's most likely in the bar, which is an easy place to find.

Castiel doesn't know if he will have much interaction with Charlie beyond this, but he's done his duty for a friend of Sam and Dean. With his work done, he takes off again, disappearing like he was never there to begin with.