Biting parrot is 90% of the time trying to defend itself, or in some cases his/her mate or nest.
If your B&G was abused in her former home, she could have a low “trust account”, which means she doesn’t trust people or she has learned, and is teached, to bite when she example wants to be in peace, sleep, eat, or do something herself. She knows backing up or telling she doesn’t like the situation in her natural way of body movement doesn’t help, only biting. Which means thats her only way of telling you that she isn’t comfortable now is by biting.
You should also remember viewing the situation through your parrot’s eyes, and especially if you want to correct the behavior. For a parrot “abuse” also means forcing her to step on your hand by pushing your hand against her chest or feet, taking her to the cage even she doesn’t want to etc. which can all be teached her by positive reinforcement, what I have done with all my parrots. They all do exactly what I want and when I want, but they do it because they want to do it, not because they are forced. I know it works because example I tell every night to all my 4 parrots to go in their cage. I say the command for every bird, and each and every one of them fly to their perches inside their cage and wait. I get the food for the night and they start eating as I close their cage. 15 minutes later the light go off. There is no way I could’ve done this by forcing them. And the parrots are happy.
Fixing this is as easy. You listen to your parrot, watch her body movement, and study about positive reinforcement. Barbara Heidenreich and GoodBirdInc. got very good videos on youtube too, also articles on the Good Bird Inc.‘s website. Incase you got urgent guestions, I can help you with them. But of course it’s important that you study yourself.