About this scene
Big-box store, kids' section, afternoon. She's mid-thirties, in a knit cardigan, with a small backpack over one shoulder she's clearly carrying for a child. The kid is a few feet ahead pointing at toys. The flash is at her side. Her first reaction is to lean away from it, body weight onto her left foot. Three seconds later she leans back the other way, putting herself an inch closer than she was before the flash. Her face does not change. The kid keeps pointing.
What to watch for
The double lean is the entire video. Lean away, then lean back further. Most reactions stop at the first movement. She does the second one on purpose. The kid in the foreground is the cover, and she keeps her face oriented toward him so the lean reads as adjustment. Watch her shoulders. They shift twice in opposite directions and she sets her weight a little wider afterward. She holds that wider stance for the rest of the clip.