Kitty Trumbull (Olivia Hussey) is the main villainess from "Sing a Song of Murder," episode 2.05 of Murder, She Wrote (airdate October 27, 1985). She is an actress performing at the Mayhew Music Hall in London; the same stage where her father, Oliver Trumbull (a former Shakespearean actor), performs with Emma McGill (Jessica Fletcher's British lookalike cousin).
Kitty had grown disappointed with her father (in her mind) settling for performing with Emma, as she felt that Emma was ruining Oliver and holding him down. With that in mind, Kitty made attempts to kill Emma, with her first attempt taking place during one weekend when she blew up Emma's gas heater. On the following weekend, Kitty placed a loose rug on the top of the stairs hoping Emma would slip and fall, which she didn't. Early in the episode (a week after the second attempt), the maniacal villainess attempted to run Emma down in an alley. The attempts led Emma to fake her death and bring Jessica to London to attend her "funeral," with the real plan being to enlist Jessica to find out who was behind the attempts on Emma's life. Meanwhile, the evil Kitty struck and killed who she believed was Emma with her car, but it was actually dresser Bridget O'Hara wearing Emma's coat.
After Oliver was freed and cleared in the attempts, Jessica revealed Kitty as the villainous mastermind behind the attempts on Emma, as she had heard Emma's phone message to Oliver after she faked her death. This proved that Kitty knew that Emma was alive and that prompted her fourth attempt and the murder of Bridget. After denying everything and attempting to tell her father not to listen to the accusations, Kitty confessed to attempting to kill Emma, claiming that Emma was destroying Oliver and she had to kill her. Following her confession, Kitty was arrested (off-screen) for killing Bridget and her various attempts to kill Emma.