Gabriella Smart (in-universe)

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

Biography
The Third Doctor was out in the Whomobile when he came across Gabriella 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, Gabriella 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.