...was Ty Lee famous? Famous as Azula's henchlady?

Did she have a title? Nobility wasn't much of a thing in the Southern Water Tribe but the Fire Nation was charmingly old-fashioned.

Would he give himself away by not using a title for the famous Ty Lee?

Or, perhaps Sokka was overthinking things. What would a lowly prison guard at the Boiling Rock know about princesses?

"We don't hear much about princesses in the colonies, ma'am," he said. When it doubt, play dumb. It worked before!