[Lauren]

On principle. She doesn't like to be made out to look a fool (i.e. when Rex took her lighter, it wasn't the fact he took her lighter - it was that he assumed therefore she was foolish).

It's the only time she gets snappy - when she thinks people are trying to make a fool out of her, or create a spectacle of her. Extraordinarily insecure.

I guess the cross-dressing task multiplied these insecurities, and once again she projected them onto others.