Auntie was composed mainly of body parts stolen from Time Lords and other creatures which found themselves in the junkyard. Uncle, Nephew and she were kept alive by House in return for doing House's bidding.
When House left the asteroid, Auntie and Uncle were doomed to die, as they both relied on it to remain alive. Uncle and she remained stoic in the face of their deaths. She casually referred to it as "time for Auntie and Uncle to pop off." She died shortly afterward and was outlived by Uncle for several seconds.
Auntie had the Corsair's left forearm and hand at the time of her death, which was recognisable by the Ouroboros tattoo which he had for each regeneration. She referred to the arm as being "a good arm for [her]." (TV: The Doctor's Wife)