Could she have eaten something poisonous? Do you use rat poison on the property, or other chemicals? Fertilizers can also cointain toxic metals. Here is a list of poisonous plants :
http://www.ca.uky.edu/smallflocks/Poisonous_plants.html
and more info on metal toxicity for birds:
http://www.birdclinic.net/avian1.htm
General signs of poisoning
http://www.petco.com/Content/ArticleList/Article/33/4/49/Signs-of-a-Poisoned-Bird.aspx
Hopefully it's something simpler and will resolve quickly. Good luck!
http://www.ca.uky.edu/smallflocks/Poisonous_plants.html
and more info on metal toxicity for birds:
http://www.birdclinic.net/avian1.htm
General signs of poisoning
http://www.petco.com/Content/ArticleList/Article/33/4/49/Signs-of-a-Poisoned-Bird.aspx
Hopefully it's something simpler and will resolve quickly. Good luck!