Happy new year to you and Irene....
She is very lucky to have you to the rescue in time. You mentioned that.....
.....she wonāt put weight on the foot.
.....Sheās using her leg, just at the knee, staying upright.
......She wonāt put her back toe over the perch proper
So, it seems her leg or foot is very hurt.
Here's what I would do....
1) Limit movement as much as possible by putting her in small cage with out perch to prevent her from falling.
2)minimize disturbance, separate her from another bird, let her rest in a quiet corner
3) provide her favorite food and water, if she doesn't eat, mix honey and warm water for her to drink every hour
4) Prepare questions to ask your avian vet....Best case.....it could be a sprained foot and she will be fine with simple pain killer. Worst case.....it could be a fracture toe or a broken finger. The only way to know for sure is by taking X-ray. You might find this thread informative.....
Post in thread 'Is there anything topical that can help with leg pain'
https://www.parrotforums.com/thread...that-can-help-with-leg-pain.91292/post-939909
5) to prevent possible repeated accident, please consider trying out these ideas....
A.. To ensure that she sleeps well through the nights without waking up to climb around, use black cage cover or move her cage to a darker corner.
B...nail trimming or use big natural wooden perch that cause her nail to wear out naturally
Please keep us posted