The star - who voiced the character for 33 years - reportedly died at her home in Los Angeles on November 30 following a long illness, reports The Hollywood Reporter.
She also starred in Days of Our Lives and The Fugutive, and played Kurt Russell's love interest in Disney's 1971 movie, The Barefoot Executive.
She first voiced Daphne the year before, joining in time for the launch of the second series of Scooby Doo, Where Are You!
Stefanianna Christopherson previously voiced the role in the first season.
She made a comeback for The New Scooby-Doo Movies in 1972 and 1973, then continued to feature on the cartoons right up until 2003.
The star lost her Emmy Award-winning producer husband H. Wesley Kenney in January 2015, and is survived by her son Kevin, stepdaughter Nina, stepson Wes and granddaughter Jocelyn.
A memorial service has been planned to take place at 11.30am on Wednesday at First Christian Church in Studio City.
Except for the headline, this story, originally published by mirror.co.uk has not been edited by SLM staff