Men notice the laugh first, mostly because it stops arriving on time. The lazy joke gets air instead of reward. He looks at her, waiting for the usual rescue, and she just gives a small smile and takes a sip.
She is not cruel. That almost makes it worse. There is no big rejection to argue with, no dramatic eye roll. Just a pause long enough for him to hear how thin the line sounded.
After that, her attention gets expensive. A compliment from her feels earned. A text that comes back after an hour does not feel careless; it feels chosen. Men start watching her face for approval before they even realize they are doing it.