butter wouldn't melt in someone's mouth

Col. Why, they say she's one of the chief toasts in town.

Lady S. Ay, when all the rest are out of it.

Miss. Well; I wouldn't be as sick as she's proud for all the world.

Lady A. She looks as if butter wouldn't melt in her mouth but, I warrant, cheese won't choke her. . . .

Col. I can't pardon her for her rudeness to me.

All unmarried women are necessarily in the market; but if they behave themselves properly they make no signs. Now there was Griselda Grantly; of course she intended to get herself a husband, and a very grand one she has got: but she always looked as though butter would not melt in her mouth.