In a parallel universe where the Doctor escaped the Time Lords by regenerating into a female incarnation, the TARDIS was abandoned and its Time Vector Generator was removed to better hide it from the Time Lords while the Doctor went out of her way to try to adapt to a human life.
Later, the Doctor was recaptured and she was later sentenced back to the TARDIS since she had embarrassed the Time Lords by escaping their justice. Originally she was to be exiled to Earth in the first place, but with the escape, it had elevated to death. She would be confined to the TARDIS to live there for the rest of her life, and if she tried to escape it would dematerialise, erasing her history.
One of the Time Lords claimed to sympathise with her plight and told her in a note she had a way out. The note told her the TARDIS was not rigged to erase her history. As she set the controls and began to leave in the TARDIS, the Doctor wondered if the note was genuine. (AUDIO: Exile)