He gives the compliment a little too directly, and the old script would have saved everybody. Quick laugh. Dumb joke. “Shut up.” Maybe a fake complaint about looking tired.
Instead, she lets it land. She looks at her glass for a second and says, “Thank you.” No scramble. No wrapping it in embarrassment so he can pretend he meant nothing by it.
The table keeps moving, but he does not. A plain thank-you can feel more dangerous than flirting when it comes late and calm. It tells him she heard exactly where he aimed it.