This is a heartbreaker

I wish you'd posted in the first few days. It's the sort of behavioral change that usually responds best to immediate, focused attention. You can still hope for change, but
you need to really tackle it hard and determinedly. I don't think this forum has enough active participants to help you, but I suggest you contact Michelle Karras at PoliteParrot.com and see if she can work with you by phone or can recommend a behaviorist who can. Whomever you select must base her behavioral work on the positive reinforcement principles of Susan Friedman.
Please hurry!
PS I've not been able to get Michelle's site to open. Maybe it's a problem at my end. Google for other ways to contact her. She's in Chicago. Also, if your 'too hasn't had a vet exam with comprehensive bloodwork in the last month, that's always the first step when dealing with any change in behavior. You want to rule out illness right away. If you need help finding a GOOD avian vet, just tell us where you are and we'll help.