butter would not melt in someone's mouth

English edit

Alternative form of butter wouldn't melt in someone's mouth
- 1861, Anthony Trollope, Framley Parsonage:
  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. It would have been very wrong to call her a marrying girl.