Okay, so welcome and so glad you are here!
If she is biting because she is about to fall and trying to hold on, that is one thing...but...
I am going to be honest here lol...Your fingers are PROBABLY suffering because you are ignoring the fact that she doesn't want to be touched by your hands (and that is her right). You are pushing very hard and very fast and harming trust. These are not like dogs or even cats, you have GOT to give them time and prove yourself--- move at their pace and read their signals..Right now, you should be focused on making yourself as low-stress and positive as possible (remember, positive to you may not be positive to the bird). For instance, if you try to hand her some millet and she steps back, that is NOT a positive interaction-- that is her saying whoa-- what is this thing in my house and I do not want it here...Birds bite as a last resort to communicate when we ignore all of their other signals and messages.
Imagine meeting a pretty woman (or man) on the street and immediately going in for a big kiss...That is likely you and your bird right now..Yes, I know YOU wanted this bird and feel like you have waited and waited, but the bird didn't necessarily "want" to go to your house (new environment, new sounds, new flock)--The bird had no idea it was going to happen until it was transplanted from everything it knew...This isn't meant to be offensive, but you have to do this on the bird's terms (not yours)...You will get nowhere by being a dictator...
Now, baby birds do need some help sometimes with bite pressure training etc-- but the fact that it is happening most to you makes me thing it is because of something you are doing.
NEVER grasp their beaks...never physically punish...never ever..In the wild, birds VERY VERY VERY RARELY bite other birds of the same species...If your bird is biting hard with intention, it is your inability to understand that behavior that is getting you bitten.
Some birds also hate hands, even if they like people, so just because she likes you, doesn't mean she is ready to be touched by you just yet.
Side note:
Remove any snuggle huts or shadowy spaces in the cage-- these are dangerous for health but also for hormones...Do not allow your bird under your shirt, in blankets, in boxes, drawers, under furniture etc...
10 hours sleep MINIMUM on a nightly sleep and wakeup routine (just like a kid)
Pet on the head and neck--any other contact should be very short because it will get sexual as your bird reaches puberty.
