Anyone who has experience rehabilitating a really aggressive bird, particularly a small one, please share your insight.
I was recently 'donated' an astoundingly beautiful and complicated little hen budgie to join my flock of 6 budgies and live in their large flight. I took her on as a, 'I'll see what I can do', project as I feel I have the potential to offer her a better life. In her previous home she was isolated in a tiny cage without any company and her people became too frightened to open her cage. Right now I have her separated in a large quarantine cage, in the same room my other budgies free-fly, while we get a handle on her issues.
A little back story. This bird was hand-fed from a young age and loved on pretty intensely. The owner has had other handfed budgies in the past from the same breeder. However, at what I'm guessing coincided with sexual maturity, this budgie started nipping. I don't know if it started as play nips or fear, and I don't know how they responded. But where it is now is pretty extreme. This bird is completely keyed into you, so if you walk past her she will follow you along the cage bars, reaching as much a possible. If you walk away she'll scream. Although I have not given her the chance to chomp my flesh in a serious way, I have no doubt she will. The second her cage is opened she'll be on you (she is flighted), looking for flesh to bite. From the complete mutilation of everything in her cage and her terrified ex owners, I'll wager it's a hard bite.
So here's where I am with her now. I've been transitioning her from an all seed diet to a pellet and fresh food/sprouted diet so I can use dry seed as a reward. She is a fast learner. She's mostly transitioned and is very motivated for spray millet as a reward. I have taught her to target which she does with gusto. I have also given her a number of food puzzle toys and shredding toys to help her with her energy, which is abundant. My budgies are greeting her through her cage everyday, although I haven't let them loose together yet. I want to start soon but she just passed two eggs, and my other hen is also laying, so I am waiting for them both to cycle through that to a lower hormonal point first. I have let her out of her cage a few times with me. She will fly to me instantly and start searching my body, it seems to be curious and playful (and probably was once) but I know she's looking for somewhere to bite. I've had the foresight to wear a wool hoody at this stage while handling her to avoid the flesh chewing. I've gotten her to move from (covered) arm to arm, back in and out of the cage with the target.
But where to go from here? She is completely motivated to be attentive to me and work with me. But without a barrier, cage, clothing etc. she seems absolutely driven to find people and bite them. I have been given aggressive birds before but the aggression was always defensive/fear based and faded when they realized they won't be forced to step up etc. I've never had a bird simultaneously desperate for human company that wants to drive away every person around. The best word I can think of to describe her is 'rage'.
Any advice? Stay the course and wait for improvement? Train her to do some tricks? Any specific advice for what to do if and when bitten?
I should mention I have had her on my bare hand once in her cage. She didn't "seem to notice' that she was standing on my hand to eat millet. But within a few minutes her eating went from normal too 'furious', where she started ripping chunks of millet and then turned to go for my hand.
edited to ad: I have no expectations of her other than wanting to give her a better life integrated with other budgies if possible. However since my budgies are all free flighted and friendly, I would be nice to be able to have her with them, and not having her flying for my face each morning when I walk into their flight to clean and feed.