Miss Clinkscales was Duke Ellington’s piano teacher when he was 8 years old. Nick assumes Duke lost his virginity to Miss Clinkscales but Duke assured him that Miss Clinkscales was sadly unmarried at 25, which was not normal at that day in age.
Marietta breaks the fourth wall to let the audience know they didn’t need to worry about her because her life was going perfectly fine with her “lady companion” Ernestine she had tons of sex with. She also joked if orgasms were money, she’d be a Rockefeller.
The real-life Marietta Clinkscales was Duke Ellington’s piano teacher, but she was not an out lesbian.