Mary Barbara Jefford, OBE (born 26 July ) is a British Shakespearean actress best known Other West End plays included Ride A Cock Horse, Filumena, Mistress of Novices and The Dark In she was in the opening production at the Olivier Theatre playing Zabina in Tamburlaine the Great with Albert Finney. Directed by Oliver Parker, Barnaby Thompson. The girls of St. Trinians are on the hunt for buried treasure after discovering headmistress Miss Fritton is related. her turn as Ben Affleck's mistress in David Fincher's Oscar-nominated Gone Girl. And then there's her career as an increasingly-super model.