About this scene
Suburban grocery store parking lot, mid-afternoon. She's loading her car at the trunk, two bags in one hand, keys in the other. She lifts her head to pop the trunk via the key fob and sees what's happening in the car parked next to her. Her face goes blank for two full seconds. The bags are still suspended. The keys are still in her thumb. She sets the bags down on the asphalt instead of in the trunk. Then she just stands there.
What to watch for
The bags on the asphalt are the giveaway. She would not normally set them down on the ground. She is doing it because her brain has reprioritized. Watch the keys. They stay in her hand for the next forty seconds. She does not pop the trunk. She does not load the car. The next-door driver eventually pulls out of the spot and her trance breaks. She picks the bags up off the ground, opens the trunk, and finishes the loading at half her original pace.