Thank you all for all of your advice! I guess it's just the extra-cautious-excited bird mom in me makes me want to be prepared for the worst. Seeing her so scared of me with blood everywhere on her first night here really took a toll on me as well as her. There has already been a decrease in her nail biting, she is taking treats from my hand, she even let me touch her beak earlier, and , as I am typing this, she is climbing down off her cage for the first time to check everything else out! Small steps are all I can ever ask for, especially from such a scary background. As someone who has seen so many rescues gone bad, I am so determined to make this one go as perfectly as possible. One good thing to come from her neglect: she has a good handful of her flight feathers back, I predict that she will be able to achieve some lift after her next molt! I will DEFINITELY need more help when that time comes due to my sheer lack of experience regarding that. You all are wonderful! Thank you
EDIT: To be clear, this means no training yet! Just making a happy healthy birdy.