Although weight loss and a poor appetite can be stressed induced, that would not be the explanation for her since she is exhibiting other symptoms of illness. The vomiting is of particular concern.
Vomiting causes can include:
- Dietary indiscretion (eating something you do not know about)
- Stomach or intestinal foreign body
- Something that was given to them (new food, new treat, human food)
- Intestinal parasitism (not just the worms, but the microscopic bugs like Giardia and Coccidia). They can cause vomiting also, not just diarrhea
- Toxin exposure would be less likely, unless you have reason to suspect exposure to a chemical.
- Less commonly, endocrine diseases like Addison’s
So, at 1 year of age I get worried she ingested something that has caused an obstruction or some other dietary indiscretion that has made her sick. With weight loss, I would also be worried about a intestinal parasite problem. Not likely worms, but definitely giardia or coccidia.
Plus, the stuffy nose. I can't rule-out a upper respiratory infection.
So, without question, she needs to get in to a vet for evaluation, basic supportive medication for the stomach, and possibly some testing to include a fecal test and maybe some belly x-rays.
Hope that information helps.