Jen's right. Kittens who stop eating can become dehydrated very quickly.

The reason she has stopped eating is because she can't smell her food. Although I would definitely get her to the vet ASAP, you can try sticking her in the bathroom and run the show on hot. This will create steam that will loosen up any gunk in her lungs and nose. Also trying heating her food in the microwave (be careful because it can sometimes heat unevenly), make sure you test it before you give it to her.