I'm reminded of David Niven presenting an award at the oscars when a streaker ran across the stage. Niven was cool as he always was, and said something about the guy not having enough to show off like that.
What he said wasn't as cool as his unflappable reaction to the streaking.

If a woman lifts up the aprons, you could say loud enough for many to hear, "Poor thing. With a (insert her worst feature here) like that, it's been a while since she's seen one."
If you say it with aplomb, she will be crushed. She will either go away chastened or get very angry and make a fool of herself.