Who said, “Your slip is showing”?

Movie scene: A flustered young woman does her best to tell-off a calm, mildly interested, older urbanite woman. After doing so the socialite quips simply, “Honey, your slip is showing” and walks into the other room leaving the younger woman nonplussed (and utterly trumped … does she dare look down?)

What movie is that? Black and white; had to be a New York apartment; had to be Bette Davis (or possibly Barbara Stanwyck.)