- You may be looking for the UNIT member.
Jac was a human that Bernice Summerfield met on Crex.
After Guy de Carnac's death, the Seventh Doctor took Bernice to a market on the planet Crex. While he went to meet Laylock to obtain the technology to make himself temporarily human, Benny found a beer tent and shared drinks with three human women she found there.
One of them, Jac, was doing research on the market for ElleryCorp, who wished to create something similar. (PROSE: Human Nature)