The hallway pause stretches one second too long

Her hand lingers on the doorframe after she has already made up her mind to go.
One foot is aimed down the corridor. Her shoulder refuses to follow. It is an absurdly small pause, the kind nobody could describe later without sounding theatrical. She is near enough for him to catch it and far enough to pretend she was watching the elevator light, or listening for somebody behind her.
Then she goes. Keys clink somewhere. A door swings shut. Somebody calls, ‘You coming?’ He is left with the worst version of it: too small to name out loud, too well-timed to let go of.
She fixes the outfit as if a hidden camera were running

The strap gets corrected right after she notices him looking. That is the part he cannot unsee.
She had a mirror. She had the black glass of the car window outside. She had the bathroom with the light buzzing over the sink. And still the little correction happens right there. Thumb under the fabric. Hair pulled off one shoulder. Jacket opened, then closed again, as though the room had suddenly changed temperature.
It usually arrives with an irritated face, which is almost better cover than a smile. A small frown says, don’t look at me. The hands are saying something far less tidy.
Her friends notice it before he ever does

Her friend catches it first. Friends always see the setup coming.
They saw how she was standing before he walked in, and they see the half-turn that comes after. The drink rises a touch too slowly. The voice drops. A smile gets pressed into the rim of the glass, hidden from the table and missing by half an inch.
That is when the side-eye begins. One friend looks at another. Someone taps a nail against a phone case. No words required.
Later, the group chat will not recall his exact line. It will recall what she did the second after it.