What does "aren’t you the one?" mean in this context?

Question

help me, please, to understand the meaning of the phrase "Aren’t you the one?" in the following context. It seems that this phrase can have any possible meaning here... My guess is something like "aren't you a sweetie" or "you look like a boy yourself". Thank you!

"“Luscious Lily!” Popping up, he clapped his hands together. “Gino’s already at his station. This can’t be your granddaughter. You’d have been ten when she was born!”

“Cicero!” Lily exchanged kisses. “Aren’t you the one? Caitlyn, this is Cicero.”

“My sweet girl.” He clasped her hand in both of his. “What a beauty! I’ll take you right back. Now, what can I get you? Your morning latte, Lily, my love?"

Nora Roberts "Hideaway"

Answer 1

I think you should be reading around the context.

Cicero has made a ludicrous complement on how young someone looks (he says she only looks 10 years older than her granddaughter).

"Aren't you the/a one" means very little. She is saying that he is a joker and flirt, but that meaning comes almost completely from the context.