She does not rush to reward a compliment. Sometimes she lets it sit there between the wineglass and the phone, long enough for the man to wonder if he phrased it badly.
Then maybe she smiles at the wrong part. Maybe she answers with a dry little “thank you” and goes back to the menu. The flirting is there, but it is not handed across the table with a bow on it.
That delay changes the room. He is no longer trying to get her attention. He is trying not to waste the bit he got.