If the feathers were pulled out, quill and all, then they would start to grow back immediately. If it was only the feathers removed but not the quill, then however long it takes to molt out those quills.
My Jayde is also missing feathers on the back of her head, and as far as I know, those were damaged over 9 months ago! A couple have grown back in, but still missing quite a few.
It could be a few weeks or it could be a year or two.
She probably stepped up fine because she's in a new environment and didn't know if she was safe or not - hence no 'cage aggression'. Now that she's starting to settle in, she doesn't like your behavior and she's biting you. Right now it's probably best to give her some time and allow her to get used to all the new things.
When Jayde came here three months ago, she bit to draw blood! Tear flesh from bones! She was *not* happy! But I was expecting that. Instead of forcing her out, I left the door open. She wanted to be with me, but was afraid of me at the same time. I walked away and she'd scream at me as well as flap her wings. I walk towards her and she'd run away and hide. I walk away again and she'd try to follow, but couldn't. Offer my hand? She'd bite! She's actually scared of hands.
I just started by moving the cage around the house to a different room I was sitting in and just allowed her to choose what to do. She could be in the cage or on top of it. Her choice, although she most often chose to be on top. Sometimes she'd come down the cage sides, but still couldn't be handled.
A few weeks later and she was tentatively climbing up onto my shoulder - again, avoiding hands and arms! Whenever she became unsure of things she'd start squawking her "I'm scared" call and I'd take her back to her cage and she'd climb back onto it. I couldn't always get her to come off the cage but it actually started with me sitting on the floor next to her cage and just giving her non-physical interaction. Curious, she'd climb down to come investigate and eventually she felt confident enough to climb on my shoulder for a few minutes at a time. Short bursts, and I couldn't walk away from her cage without her freaking out.
Three months of having her, she's still afraid of hands! But she's starting to get used to my arms now and willing to step up on them rather than biting them. She tries flying to me, but she doesn't have her flights fully grown out yet (i.e. clipped feathers molted). She's much more comfortable leaving her cage and getting slightly more comfortable about not being on me if she's not on her cage. She still has a while to go, but she's getting there. She's becoming comfortable enough that her insecurities and fears are not as strong as they used to be. When she bites, it's more of a warning bite than a bite meant to cause serious harm. (of course, I've been trying to avoid getting bit anyway!)
She will come to me without hesitation when she's ready to climb aboard, although sometimes I have to butter her up first!
There's even times that when I go to take her back to her cage, she wont climb off! Or if she gets scared and wants to go back to her cage she'll climb off, only to turn around and climb back up on me! She just needed that moment to feel "better" then it was back to what we were doing before!
