Although Ms. Duncan had been forced to concede defeat on the door, she still told Clare that the dress was too short. She also told her she'd be watching her. Ms. Duncan's advice to Clare was to make sure she kept the dress pulled down, and be careful about how she stood or sat.
In conditions such as this, it was very difficult for Clare to enjoy the prom. Could you really have enjoyed a night out if you knew someone was watching your every move?