She was portrayed by Stella Tanner.
Lois Leffour reveals that she is from Southampton in England. Like all witches, her main hobby is murdering children, due to the fact they smell like "dog’s droppings” to her. When she goes to The Witches annual meeting at a hotel, she reveals what her true form looks like (She is bald and has scaly claws covered by gloves). When the Grand High Witches demonstrates how her new formula 86 turns Bruno into a mouse, Lois is shown cackling with delight.
When the witches smell out the boy hiding in the room with them, Lois is one of the main witches to give chase. Lois meets her downfall with the other witches. Ironically they consume formula 86 after it was put in their soup by the boy and his grandmother (who had been turned into a mouse). After being transformed into a mouse, she was slaughtered by one of the hotel staff members, believing her to be a real mouse.
James and the Giant Peach
Fantastic Mr. Fox