She could well have allergies to her food. Friskies isn't the best food out there to begin with.
Try changing her over to a better quality like Royal Canin.
There is a lot of information in this forum on foods and the quality of foods. Go to some of the threads and do some reading. There are also threads regarding allergies to food which you should be able to find easily.
BTW - when you are changing over foods, you usually have to do it gradually, i.e., mix a bit of the new food in with the old and increase the amount of new food every day until you have completely changed to new food (about 2 weeks).