She was born on 23 November 1948 and celebrated her 15th birthday on the day after Susan, their science teacher Mr Chesterton and their history teacher Miss Wright disappeared. She met the First Doctor on at least one occasion, but the Fourth Doctor did not recall ever seeing her before. He also did not remember Susan ever mentioning Debbie but admitted that he was not always the best listener.
The Doctor offered Debbie the chance to travel with him, telling her that he could show her the crystal temples of Canopus or the signing of the Magna Carta in June 1215, but she declined the opportunity. He told Debbie that Susan decided to stay on 22nd century Earth but then amended this by adding that he chose for her, expressing the hope that this decision was for the best.
For her birthday, he gave Debbie a framed black and white photograph of Ian and Barbara standing by a police box, waving at the camera and hugging each other. The frame contained a plaque that read simply "1965." Debbie was thankful that she met the Doctor as, while she knew that she would never see Susan again, she could at least live her life in the knowledge that she was safe in the future rather than spend it wondering what happened to Susan and fearing the worst. (PROSE: Those Left Behind)