She is trapped in the grocery store along with many patrons and other staff when the Mist appears and engulfs the town outside. It is unknown whether she became one of Mrs. Carmody's followers or remained neutral.
Sally stated that when she and Jessup were in high school, Jessup flirted with her, but never asked her out. She also had an unknown family who was at her aunt's home in Boston when the Mist appeared. She was also Billy's babysitter, and apparently a friend of the Draytons. She kindly greets David as he enters the market, and is later trapped inside when the Mist spreads across the town outside.
During the first night, in the staff's locker room, Jessup admits his feelings for Sally, and the two kiss. Minutes later, Pterobuzzards and Scorpion-Flies break into the store. A Scorpion-Fly stings Sally, and, despite Jessup's efforts to save her, Sally's neck swells up, closing off her airway and suffocating her.
Sally was kind and friendly to David, and appeared to get along very well with him.
Bud and Sally were very aggressive towards one another when one provoked the other.
In the film, Jessup had a crush on Sally in high school, but couldn't find the courage to ask her out. When she was killed by a Scorpion-Fly, Jessup was heartbroken.