I would first suggest trying to check if she is sick or injured. Being hurt can manifest in many ways in rats, and aggression is one of them.
Have you gotten any new pets, clothing, etc lately, or been around any new animals? I've had rats that would attack my hands if I smelled like any of the stray cats outside, or if I played with the dog and didn't wash my hands.
Check for injuries if possible, using thick gloves will help you handle her.