This section is for emergencies or currently sick Yorkies.
She is currently sick, so I say go for it.
Where is she scratching?
Her stomach? Sides? Ears?
Typically food allergies cause itchy ears, chin and paws but it could still be that. I wouldn't be surprised if it was a food allergy because she has been fed one food for so long and maybe her body is now trying to say that it has had enough of it. If it isn't her ears though, I would look at other causes too.