I wonder,, because of that "trauma" when her parents refuse to feed her, and you stepping in, made her to addicted and afraid to lose you.
So that's why she still begs for food. She need the act more then the food? And also she don't like other birds because that remind her of negative things, and so far other birds hasn't giving her anything she needs at all. (only the opposite)
Just a theory..
That´s very interesting.
I know that some lone birds can be like this when introduced to other birds as they don´t recognise themselves as birds. But Adelie has grown up with the other birds. Everyone is in the living room, and the elders come over during flight time to check out the new thing in the room.
Adelie was fine when she was with Blue, I´m even feeling a bit guilty now for not keeping that bird!
Even very small, Adelie would take on her mum.
Here are my flock dynamics:
This shows how the bird on the left reacts towards the bird on the right.
Aldora, Lapis and Adelie
are all female, Nube and Jaime are males, Sydney is androgynous.
Red=Standing ground and attacking if someone gets too close, and staying put if attacked and retaliating. Requires intervention.
Blue=will fly away if the other is giving the warning signs of a bite
Green= there´s a love bond, but will fly away if squabble
Big problems occur when there are red lines going both ways for two birds. If I leave them together they won´t stop.
As you can see, Adelie will stand her ground and attack everyone, the problem is Lapis and Nube do the same, meaning, I have to be there to stop it.
I still let Adelie out with the flock for a bit. But I have to focus on her, meaning I´m not focused on Adlora and Sydney.
The grey is undetermined. But I think Aldora will have a red line. I can´t imagine her flying away if attacked by Adelie.
Here is the same chart but I´ve taken away adelies red lines:
A huge difference. This is how our flock was - very managable. The unit worked well. The only issue was Aldora and Syndey. So I would keep my eye primarily on them.
The blue team are pretty solid, and never create any problems amongst themselves.
I´m really hoping something improves with Adelie and the flock, Even if she just flew away if attacked or stopped attacking others.
The other day she flew up where Lapis was sat on top of my tall cabinet and tried to land on her and attack her. It´s the only place I can´t reach so I had to bang the cabinet to avoid a fight. Something I didn´t want to do as I had Aldora close to me
Lapis wasn´t anywhere near me nor had been that day ´til that point so it couldn´t be jelousy.. I just don´t get why Adelie would fly (flutter) 2-3 metres away to attack Lapis for nothing.
There´s so much conflict around her. Not just that she attacks everyone, but most will attack her.
Her flight still isn´t great so I let her out for about an hour then put her in her cage.
Maybe when she´s mastered her flight and is weaned things will change... I really don´t know.
pretty pretty bird.
I'm sure she'll do a lot more than that in there. What cage did you get her?
that hopefully soon is weaned. 
