Mrs. Ellen Sharp is a certified witch who lived downstairs from the Chant family in Wolvercote.
An older lady without much education, Mrs Sharp is not a very successful witch, so she does many little things to make ends meet. When the elder Chants are killed in a paddle steamer accident, leaving the two children among the survivors, Mrs. Sharp volunteers to look after them, which she does, pocketing bits of money here and there from the Fund set up by the town to support them. She makes gingerbread men, but very badly.
Mrs. Sharp has a wide circle of acquaintances in Wolvercote, including the Willing Warlock, the brothers Henry Nostrum (necromancer) and William Nostrum (wizard), as well as Miss Larkin the fortune-teller and her brother, the Mr. Larkin who runs a shop. She manages to find a way for Gwendolen to take magic lessons under the guise of studying music. Mainly, her interest is in how she can tie her wagon to Gwendolen's star and profit by it somehow, but she is also fond of Cat and he is vaguely fond of her. When he is taken off to the Castle, he promises to write, and in his early days there he feels quite homesick for her.
At the CastleEdit
At one point, Cat and Janet are so frightened of various people who are after them (believing they had done some of Gwendolen's wicked magic tricks) that they run away from the Castle, thinking they will seek refuge with Mrs. Sharp. They are brought back by a worried Millie, but later Mrs. Sharp does come to the Castle to pay Cat a visit. She shows a lamentable tendency to want to steal silverware, and is overall so shabby and weak that Janet has to tell Cat that running away to her wouldn't have done them any good. Cat, by that time, has realized that himself.