Boger touched on this a bit... but a little more clarification
After the first 2-3 meals, a typical ball python should be eating small mice. I have the feeling that she's getting a bit nippy not just because she smelled food, but because she may not be getting a large enough meal as well.
Don't look at the size of her head as to what you will be feeding. A fuzzy, while the size of her head, is a very small meal.
She should be eating something that weighs around 10% of her body weight. And if she is 2 feet long, then she is getting far too little to eat from a fuzzy mouse. A fuzzy rat is maybe about right. If you don't have a scale available to weigh her, another thing to do is eyeball the size of the mouse compared to her girth. The meal should be about the same size as her widest point on her body, even slightly larger is still okay.
Because she's been eating smaller prey, if she was my snake, I would up to the small sized mice for at least a couple of weeks before possibly even jumping to a medium sized after that. Don't shift the size of the prey too much too soon. You don't want to risk a regurge.
I would also consider waiting until after she sheds to also avoid the risk of regurge.