A lady considers that it is possible to be thoughtless
when expressing a compliment.
For example, if in front of Ann, Mary admires Grace's dress, then Ann may be left to conclude that hers did not merit a compliment. For this reason, Mary, if she is a lady of courtesy, will wait to compliment Grace privately.
Principle: On matters of dress or appearance, a lady does not compliment one individual in a group.
Art: Painting by Edmund Tarbell, 1880