Sally Hemings is personified on stage but has no lines in Hamilton. She is seen in the first song in Act II, What'd I Miss? Thomas Jefferson asks her to open the letter on his desk, calling her "darlin'", betraying their close relationship to the audience.
In The Hamilton Mixtape, Sally Hemmings is referenced again by Alexander Hamilton during Cabinet Battle #3, first indirectly by accusing Thomas Jefferson of being against the government freeing slaves because he would be unable to find another mistress, then calls her out by name, saying that Jefferson wastes times and avoids the issue while he remains in a relationship with an enslaved woman.
"Sally, be a lamb, darlin'. won'tcha open it"
— Thomas Jefferson. "What'd I Miss""All your hemming and hawing, while you're hee-hawing with Sally Hemings"
— Alexander Hamilton, "Cabinet Battle #3"