With an effort of will, Rosapia does not frown. To frown would be to alert this man. Instead, she puts a pleasant half-smile on her face, and tries to figure out what she can about him while she casually follows.
"Ho there!" she cries to him in Common. "Forgive my forwardness, sir, but those are some fancy clothes you wear. Might you tell me a little bit about them?"
Bardic Knowledge check: (1d20+6)(22)
Bluff (1d20+7)(12) for the purposes of not alerting him that she's interested in figuring out if he saw her. She is actually a bit curious about the clothes, but of course the main thing is whether he saw/overheard her.
Sense Motive (1d20+10)(21) to see if he reacts like he saw her earlier.