I dont know much about greys but i'd say, get a nice small second hand cage and that should be her time out cage, nothing in there but one perch to sit on and a water cup. She wont be in there forever so dont put food in.
Her other cage has food and water and toys and she feels safe there, taking her out of there and placing her into a place where she has non of it would let her sit and "think" for the ten to whatever minutes you placed her in there.
Taking her out and if she is nice talk to her when she cant see the small cage anymore, very important you dont want to praise her for being in that cage. Then you can try if she is nice you can try offering her a treat, but not directly after she has been in the time out cage as she will associate that with treat time.
Then look at what mood she is in, when she isnt in the mood for you place her in her good cage, but keep on talking to her and interacting with her.
You dont by any chance put your fingers through the bars to touch/pet her?
She will soon begin to show you when she wants out or not. You say she bites when stepping up? Does it happen when you put your hand in the cage? If so try to let her come out on her own, and take it from there.
Sorry long post again, hope you can manage this problem, Kodie was also a bit cage aggressive, but he got over it. Let us know if there is any change and what method you tried and worked for you.
