If no one has been raising their hand in anger to her, it may not be completely behavior-related...Have you had her to the vet for a check-up? Maybe an ear infection and she's worried you'll hit the sore spot or something? Sudden behavioral changes in dogs seem to go along with medical issues a lot of the time (remember, they can't just say, I've got a headache, or earache, or whatever.)

Good luck!