I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. I'm afraid that Kristie's weight loss, lethargy, and now loss of use of a leg suggests a grave prognosis associated with cancer - an expanding abdominal tumor now pressing on the nerves innervating her leg, e.g - a pathological fracture of the leg due to a nutritional imbalance, egg-binding and resultant obturator nerve compression, or perhaps a metabolic disorder causing a central or peripheral neuropathy (nerve disorder). The primary etiology of her decline would need to be clarified by an avian vet (please see here: www.aav.org) but I must admit that considerable supportive care will be necessary before Kristie could be stressed by diagnostics which could include blood and droppings testing and X-rays.
Can you tell me, please, what treatment she received from the ER vet? Was a tentative diagnosis given to you? Until Kristie can be attended to, please heat up her environment to 85F by means of a 100W bulb shined into her partially covered cage (not at night when she needs to rest) or by taping a heating pad set on its lowest setting to the sides of her cage. Remove her perches and put her food and water on the bottom of the cage along with her. Add a water soluble avian vitamin such as Oasis brand to her water at half of the recommended dose so as not to make her water distasteful. Add a calcium supplement such as Calcivet or Calciboost to her water. These supplements are available in pet/feed stores. Avoid over the counter antibiotics designed to be placed in her water. They won't be effective if only because an ill bird won't drink enough to medicate itself properly.
Nutritional imbalances are a common cause of illness in our pet birds. What has Kristie's diet consisted of, please? Seeds should compose less than 20% of her diet. Ideally, a balanced pelleted diet such as can be found here: www.harrisonsbirdfoods.com or here: www.lafeber.com/pet-birds should be fed as well as hard boiled egg yolk, pancakes and cornbread, the tops of fresh greens, dairy products such as yogurt and cheese, fresh fruits such as apples, pears, melon, kiwi, and berries, vegetables such as broccoli, carrots, beets, asparagus, cabbage, sweet potato, and squash, and even tiny pieces of meat.
Please respond with further questions or concerns if you wish.