Article continues below advertisementCass Elliot Was 'Unhappy,' Author ClaimsSource: @ITS LULU- BBC STUDIOS TELEVISION The Mamas & the Papas rose to fame in the 1960s. Article continues below advertisementCass Elliot Died at 32Source: MEGA Cass Elliot died in her sleep. Elliot died in her sleep on July 29, 1974. Article continues below advertisementCass Elliot's Daughter Debunks Wild Death RumorSource: MEGA Cass Elliot's daughter firmly denied her mother died from choking on a sandwich. Source: @Russell Harty Plus/ ITV,MEGA,@ITS LULU- BBC STUDIOS TELEVISION Cass Elliot's daughter said the rumors about her mom's death were 'horrible.'