Gabriella Smart (in-universe)

Gabriella was the sister of David, and performed an act that involved dogs at his circus.

Biography
The Third Doctor came across her crying in the road because she had lost all of her dogs. He helped her to find one of them, then drove her back to David in the circus. However, she had only found one of the dogs, so she and the Doctor went off to find the rest of them. (TV: Billy Smart's Children's Circus)

Behind the Scenes
Gabriella Smart portrayed herself in the television story Billy Smart's Children's Circus.