Sally and her sister were abducted shortly after the Great War, which means she is over 200 years old. Her parents were killed almost immediately after the war, leaving the two girls to themselves. After the abduction, the girls were separated, and Sally never learned that her sister died during one of the aliens' many experiments. She's blocked out most of the bad things that happened to her. Now a fixture in the lower levels of the ship, Sally has repeatedly escaped custody and explored a good deal of the ship's lower level. She has a degree of insight into the workings of the mothership and the motives of the aliens that nobody else possesses. Aside from being a trusted ally, Sally also offers random alien items if the player requests them, every few hours.
After completion of the quests, Sally stays aboard the alien starship and scrounges for materials. The player can return to the starship at any point and ask if she's found anything, and, if she has, she will give the items away. This interaction can be manipulated the same way random encounters can be manipulated. The player can also simply wait 24 hours and ask her again, and she will give away more items.