Heidi Slitheen

Bloorm Vungah Bart Gossimar Day Slitheen was a female member of the Slitheen family. Bloorm, her husband Dax Fex Fize Slitheen and Korst Gogg Thek Lutiven-Day Slitheen offered to help the Xylok race destroy Earth in exchange for their revenge. Eventually, she teamed up with Sarah Jane Smith to stop themselves from being crushed by the double-crossing Xylok, Mr Smith. In the end, they left Earth.

Biography from the TARDIS Data Core article, licensed under CC-BY-SA