Upon graduating in the 1950s, she began working in the animation paint lab of Disney Studios on films, including Peter Pan.
[1] Sullivan returned to Disney around 1987, animating such films as Oliver & Company (1988), The Little Mermaid (1989) and The Prince and the Pauper (1990).
In the 1990s, she painted cels for The Lion King (1994), Pocahontas (1995), Hercules (1997), Tarzan and Fantasia 2000 (both 1999).
She taught art to children in the neighborhood of La Mirada, California where the family lived.
[3] Sullivan spent her remaining years residing at the Motion Picture & Television Country House and Hospital, where she died of complications from COVID-19 on April 13, 2020, three days after her 91st birthday.