It sounds like kitty acne and that is nothing to be concerned about. I ahven't had to deal with it but I think others have said to wash the chin area with peroxide and don't use anything plastic for her food or water. For some reason plastic is a problem and you should only use glass.
Others will be able to suggest more but I really wouldn't worry. It's not a horrible thing and it won't hurt her. Hang on for the experts and they will tell you how to treat it.