About this scene
Mall corridor, mid-evening, light foot traffic. She's a thirties shopper, casual outfit, two store bags in one hand. The flash happens at her one o'clock as she rounds a column. Her free hand goes to her mouth involuntarily and stays there for four full seconds. She does not move otherwise. Her bag drops one strap off her shoulder and she does not adjust it. After four seconds she lowers the hand, blinks twice, and walks around the column without looking back.
What to watch for
The four-second freeze is the duration that sells the reaction. Most reactions are over in under two seconds. Hers extends into uncomfortable territory and you can see her trying to remember to move. The hand-to-mouth is automatic and she does not lower it on her own timing. It comes down only when she starts walking. The bag strap stays loose for the next ten feet of corridor before she finally fixes it. By then she's already past the column and out of frame.