Carla Langer

Carla Langer is the ex-wife of Paul Langer, and mother of Clyde Langer.

Either, her mother (most likely since Clyde mentioned not knowing his father) — Clyde's grandmother — lived at Lavender Lawns and tipped off Clyde on strange happenings therein. (SJA: Eye of the Gorgon)

Clyde was explained to have been with her during the events of Earth's transportation to the Medusa Cascade and its subsequent invasion by the Dalek fleet. (DW: The Stolen Earth)