I'm going to try and share everything I can think of to help.
You need to think of her as an ICU patient.
She is resting like that because she is so weak she us trying to conserve energy anyway she can.
So you need to help her conserve energy.
She needs 12 hours uninterrupted sleep.
If the back of her cage can't be against a wall. Use a white sheet to drape the back. This way she doesn't have to stay alert to things coming up behind her. And it still let's light through.
Put a water and feed dish right next to the spot she is useing to rest, and support herself. She doesn't need to waste energy moving yo get water or food.
Try nit to stare at her or check on her to often. She needs every nap she can take. And watching her or hovering will tax her.
Supporting warmth. Its worth it to buy one if the things for parrots , you will get a lot if use out of it. Burds are filled with all thsescsirsacs and it takes a ton of energy fir them to keep warm. Im to tired to look for the documentation I have on that. But it can't be stressed enough. Her environment needs to be over 80. It also seems to promote healing in birds.
Try and make routines and predictability, if she knows what to expect she can relax the rest of the time.
Try and keep the house calm and quiet.
She us new to your home, and fighting for her life. So she is going to be stressed, and in gaurd. So you are trying to limit thst every way you can. And help her conserve her energy every way you can as well.
I always offer a millet spray for sick burds. Its higher calorie, easy, and gives them something to pick at, you csn weave in the bars right next to her. Even big parrots seem to like it.
Ok all I can think of right now.
I so want you to be able to save her.
No matter if she acts stronger tomorrow, still do everything possible to conserve her energy.