Danielle Spencer starred as Dee Thomas on What's Happening!! from 1976 to 1979. Costar Haywood Nelson publicly announced that Thomas died of cancer at age 60 on Mond

Danielle Spencer, the actress best known for playing the quick-witted little sister Dee Thomas on the 1970s sitcom “What’s Happening!!” died on Monday at a hospital in Richmond, Va., her brother announced on Instagram. She had previously been diagnosed with breast cancer and undergone a double mastectomy and emergency surgeries. She was 60.

Danielle Spencer, who played the precocious youngster Dee Thomas on the 1970s ABC sitcom What’s Happening!!, has died. She was 60. Spencer died Monday in a hospital in Richmond, Virginia, her What’s Happening!! co-star Haywood Nelson told The Hollywood Reporter .