Nemini was second-in-command of the Optera on Vortis. She was a member of the group of Optera led by Ian Chesterton, Vrestin and Hetra who went to find a route to the surface.
She later sacrificed her life by blocking a flow of acid with her body to prevent it from flooding the Optera's tunnels. (TV: The Web Planet)
Behind the scenes
Nemini is male in the novelisation.