cage aggression due to feeding in the enclosure is a myth.

You say she's being nippy? Are these defense strikes or feeding strikes? (when she's nipping, is she recoiling quickly, or is she staying and constricting?).

Do you clean her cage and cage accessories often? The few times i have had problems with some animals being a little trigger happy is when their cage still smells like rodents the day or two after feeding. A quick cage cleaning has them acting just like normal because they no longer smell food. Or when the animal is a new acquisition and is still settling in. (but thats a different issue all together).

has something changed in her environment? Has she grown and you haven't upped her prey size? If you give us a little more information we may be able to help you better diagnose the issue.