She lights up when you arrive

Watch the first half second after you walk into the room. Before her face arranges itself into whatever greeting it's going to produce — the smile, the wave, the casual 'hey' — there's a brief involuntary flicker. A small brightening. Something in the expression that happens before she knows she's making it. That flicker is the honest one, the unrehearsed signal that the nervous system sends before the social performance can catch up and manage it. If that half-second flicker is bright — if there's a visible lift in her eyes, a relaxation in her posture, a warmth that arrives before she's decided to put it there — you have your answer. Everything that comes after is interpretation. The involuntary first moment is data. Practiced observers catch it reliably. The rest of us catch it by accident, usually just once, and spend a long time afterward trying to decide whether it was real. It was.