Generally a cat's ears will feel warmer to us. That is because their normal body temperature is warmer than ours, and any excitement or stress can cause them to be even warmer. While it COULD indicate a fever, it may be nothing at all. I suggest you take her temperature, (which is not fun) and if it's over 102, call the vet. Be careful while doing this, though. If you are too rough pushing in the thermometer, you could damage the rectum.