About this scene
Grocery store frozen section, late morning. She's in jeans and a fitted top, shopping cart half full, hand resting on the handle of the freezer door. She has a list crumpled in her free hand. He flashes from the cross aisle. Her grin starts in her eyes a full half-second before it reaches her mouth. By the time the smile finishes she's already let the freezer door close on its own. She does not stop smiling for the next thirty seconds.
What to watch for
Watch the smile spread. Eyes first, then cheeks, then mouth. The progression is slow and you can time it across three full beats. The freezer door closing on its own is the small detail that tells you she's stopped paying attention to her shopping. Her cart does not move for the next minute. She's holding the list still but no longer looking at it. She does not approach. She just keeps grinning at her cart.