Larna

Larna was one of the Doctor's best students at the Academy when he taught on Gallifrey.

Biography
Larna developed a relationship with the Doctor during her time at the Academy and commited suicide with a knife to try and stop the Doctor leaving for the Station. She was later resurrected by Omega at the Doctor's request. Larna the set off to tidy up the “side-effects” from an incident which caused history to change. (PDA: The Infinity Doctors)