I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. Which type of bird is Shelly, please?
It's important to note that once a pet bird acts ill it's already quite ill and in need of the attention of an avian-oriented vet (please see here: www.aav.org). This is a protective mechanism because sick birds are attacked by other birds in the wild and within the flock. Shelley's symptoms of poor circulation (cold feet), fluffing (an attempt to conserve heat and energy needed to maintain body temperature), vomiting (more likely)/regurgitation, and diarrhea (pasty butt) are important symptoms but they're not pathognomonic (specifically indicative) of any one particular disorder. My primary concern is a gram negative bacterial contaminant in her GI tract which will necessitate a systemic antibiotic given either by injection in a hospital setting or directly into her mouth by you at home. There are quite a few possible causes of such GI distress including bacterial, fungal, viral or toxic enteritis (inflammation of the intestines), intestinal parasites, proventricular dilatation disease/avian bornavirus, chlamydiosis, and liver disease (particularly if her normally white urates are green).
An avian-oriented vet might first treat symptomatically and supportively by providing supplemental fluids and electrolytes by needle and tube feeding a "recovery" food. Blood tests and cultures of Shelly's choana - the slit between her oral cavity and nose - and cloaca (vent) may be taken. Whole body X-rays can be helpful as well.
Until she 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.
Nutritional imbalances are a common problem in our pet birds. What has her diet consisted of, please?