Who is Miriam Whitelaw from Playing for the Ashes and what is their importance?

Miriam Whitelaw is a rich woman who is obsessed with Kenneth Fleming. She first meets Kenneth when he is her student, and later, after her husband's death, reconnects and offers Kenneth a fantastic job. She also convinces Kenneth to leave his wife and move in with her. When Miriam finds that he is having an affair with Gabriella, she's having none of it. Thus, she tries to kill Gabriella and inadvertently kills Kenneth instead.