Actress Shirley Mitchell has died of heart failure in her Westwood, Calif., condo, TMZ reported Wednesday. She was 94. Mitchell is the last surviving adult cast member of the 1950s sitcom "I Love Lucy." She played Marion Strong, a close friend of Lucille Ball's character, Lucy Ricardo, on the beloved show. She also appeared on the hit series "Bachelor Father," "The Beverly Hillbillies" and "Petticoat Junction." The Ohio native married songwriter Jay Livingston in 1992. Livingston died in 2001.