Offer her a variety of canned cat food, baby food, cheese, or tuna. If she still refuses food you can try force feeding her a small amount of a gruel made from water and canned cat food or baby food. Force feeding cats can be very traumatic for the cat and often unsuccessful--they can spit food out, etc. If she is vomiting I would not force feed her as this will most likely make her vomit more. I would contact your veterinarian and ask if an appetite stimulant or anti-emetic (anti-vomiting) can be prescribed while you are waiting for test results.
Your kitten may not be feeding due to gastrointestinal problems, infectious disease, severe intestinal parasitism, feline upper respiratory infection, or other congenital diseases. The mother also may have decided to stop feeding the kitten and now the kitten is too weak to nurse. Kittens at this age are very fragile and fade away quickly. Typically they die from the secondary effects of dehydration, hypothermia, and hypoglycemia. This kitten needs to be examined by a veterinarian to assess health status. You will also have to start tube feeding or force feeding this kitten. Kittens cannot survive very long at all once they have stopped eating.
Get to the vet of course. I nearly lost my 6 year old cat when she stopped eating. She developed fatty liver disease because of that and the only way she survived was from about six weeks of force feeding. Vet told me to have a feeding tube put in, I did not. It took a lot of time and effort - she too was vomiting. The secret was getting enough food in her to keep her alive and that was not easy. Be sure to get advice on force feeding if it comes to that. Don't wait too long though.
