In the novel "Scarlett" by Alexandra Ripley, Mammy is said to have died from old age and a broken heart. She passed away peacefully in her sleep, feeling content that Scarlett was finally happy and settled in her life.
Hattie McDaniel was the actress who played Mammy, a perfect
characterization of Scarlett's mammy, who kept her in line.
Scarlett would ignore orders from anyone else than Mammy, and Mammy
knew Scarlett well and accompanied her to Atlanta from Tara because
she knew Scarlett would get in trouble.