Lucie Miller
Lucie Miller’s life is a complicated one. Thrust onto the Doctor by the Time Lords, she was forced to stay with him (and him with her) until they lifted the lock between the TARDIS and her. She stayed with him until he was apparently killed falling to his death with Morbius. 600 years later (for him) they me again, and travelled once more until a terrible secret was revealed and she left him, apparently finally. Out of chance, they met again on Mars, before a final battle with the Daleks. To the death.