Sally was a shopkeeper in Thisis. At least two incarnations of the Doctor visited her regularly whenever he was staying at his country home in the area.
The Second Doctor had told her that a new man calling himself the Doctor would be coming to her shop someday instead, saying he was his brother. This is who she believed the Third Doctor to be. Sally did not believe his stories of alien invasions until Verdigris made robot sheep attack her village. At that point she was sixty-seven years old. (PROSE: Verdigris)