So, did your parents leave her out and she got lost, or something like that?? It seems odd that she was "found" in a shed with a part of a collar. Thank goodness someone was able to get in contact with you. Poor thing. She really needs to be pampered and taken care of in her old age, and be an indoor cat. Get her to the vet, get some Revolution or Frontline on her, and giver her lots of love and really really good cat food that will get her back in tip top shape!