Whenever a bun has a dramatic behavior change my mind goes to a medical issue. Buns are so good at hiding pain, that there might just be one symptom.
Molting can definitely make buns moody, but if that’s not the case, I would have a thorough check up at the vet just to rule out anything.
Dental issues especially can have weird symptoms, and might make her not want to be stroked (if her face hurts). I had a bun with crazy dental issues and he was always very reluctant to have his face touched.
The other thing it could be is a strange scent. Has anything changed in your day outside home? Maybe a co-worker bringing their dog in, or something else that might make you smell weird to her?
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.