Anna (Soul Mate)
From Tardis Wiki, the free Doctor Who reference
Anna was a human from an Earth colony that had been attacked by aliens. She was the only survivor.
Several centuries later, the Fifth Doctor, Nyssa and Tegan were drawn to the colony by a psychic event. They encountered Anna, who took Tegan prisoner to keep her company. After Tegan escaped, the Doctor told her that, though they thought they saw Anna, she wasn't real — she was an imprint on reality. (PROSE: Soul Mate)
