There is a bug which prevents Wilba from turning back to her normal form after a full moon night. Due to the fact that this is not caused by eating monster food, she will not turn back after 1 day. However, she can eat a piece of monster food to go back to normal, or wait for the next full moon night to end.
1. Wear the Silver Necklace before full moon comes 2. Wait till the night phase is about to end 3. Take off the silver necklace 4. It will be daytime by the time Wilba finished her transform animation 5. Wilba is still in her werepig form in daytime