Diana (Mousie) Powell, former actress and widow of the late film star William Powell, died of cancer Jan. 18 at the Eisenhower Medical Center in Rancho Mirage. She was 77.Born Maebelle Lewis on Sept. 18, 1919, in Asbury Park, N.J., to a show business family, she played the vaudeville circuit as a child. Under the name Diana Lewis, she appeared in numerous films for Paramount and Metro-Goldwyn-Mayer, including “Johnny Eager,” “Andy Hardy Meets a Debutante” and the Marx Bros.’ “Go West.” She met Powell, the debonair star of the “Thin Man” films, at an MGM Thanksgiving party in 1939. Powell told the 5-foot-1 actress she looked like a little mouse, and the nickname stuck. They were married in 1940. The Powells celebrated their 45th wedding anniversary in Palm Springs in 1984, shortly before William Powell’s death at age 92. She is survived by a sister. Contributions in Powell’s name may be sent to the Living Desert, or to a charity of the donor’s choice.