Chewing off feathers (barbering) is not usual molting behavior. It is usually the beginning of a lifetime of feather mutilation. The sooner you can try to stop it, the better chance you have of it not becoming a permanent habit. Try everything you can think of. Rotate her toys daily, give her unusual foods to eat and play with, give her things that can be chewed and destroyed (wood blocks and old computer keyboards). Do not give her any kind of attention when she is chewing. Turn your back on her until it stops.
Be sure to preen her head feathers for her. They might be itchy and bugging her since she can't get to them and doesn't have a flockmate to take care of it.
Two of our rescues (one umbie and one moluccan) barber their feathers. Who knows how long they did it before they came to our home??? It is such an subconscious habit they even do it when they are being cuddled.
My U2 snips her wing feathers off and plays with them like her favorite toy. When she runs out of her own feathers, she snips feathers off the other birds. We have tried everything! It is heart-breaking and frustrating. Who knows what causes it, but from what I have observed, its almost as if they don't realize what the feathers are for. Like they weren't raised around any other birds who could show them how to preen properly.
Also: be careful handling her in this state. When they are missing their feathers, they are off-balance and if they fall, they don't have wing feathers to help soften the fall. They can get injured much more easily.
Good Luck & Best Wishes, Cari