When does Emily realize the difference between the alive and the dead?

In the final scene, Emily, who has loved George very deeply, has attained a detachment and serenity that the living do not possess. She can therefore observe George's grief without any of the passion of the living. She simply comments that the living don't understand. Thus, Wilder uses Emily as an example of how the average person can live, marry, and die before comprehending the potential of life.