[Birds Are Beautiful]

I have a female cocktiel, about 2 years old. I raised her from an egg. She started plucking, about 6 months ago, and hasn't stopped. She still has feathers on her wings, but her body, is almost compleetly bare. I have taken her to an Avian, and after 4 months of visits, tests, and RX, still no relief. An Elizabethan coller was discouraged, because it can stress out a bird, and the itching of new feathers coming in would be anoying to her. She would be more stressed by this the Avian told me. I took her to another vet, who has an avian on staff, and the same thing. I feel so bad for Maxine, but I don't know what else to do for her. Is there some medicine, or treatment, that has helped a plucking bird in the past? I give her Aloevera baths, by spraying her. Nothing seems to work. I have 6 other cockatiels, and none of them have this behavior. If anyone knows if there is something to suggest, please let me know. Regards, and Thank you for any suggestions.