Morning Marta, I rescued a grey a few years back, who my vet said had had some sort of head trauma, she however was calcium deficient too and had other problems, she couldn't climb her cage cos her brain wasn't engaging with what her feet did, if you know what I mean.
Firstly I would as the others say take her to your avian vet, get her checked out so you have a rough idea what you are dealing with.
My Myrtle we know now was probably an x aviary bird, our vet thought that she had fallen off her perch because of lack of calcium, hence the other injuries, he didn't hold a lot of hope out for her, we kept going back and forth but decided no more as it was traumatising her more as a he hates being handled.
I adapted her cage, she hated toys, I raised the bottom up so she could still be at to he height she wanted to be, I got rid of the grill and padded the bottom out it used to be with towels and paper on the top so if she fell it was a soft landing, I put her a perch in and she also had access to food and water low down and where the perch is, her cage has all horizontal bars so she can still grip. Everything has been done on Myrtles terms, not on ours, she came out when she wanted to, we never forced her (we had to towel her to get her back) she couldn't fly cos she snipped all her flights and then when they were growing back through she would panic and snap them again. She has also had vitamin supplements I use nutrobal
I could go on for hours about my girl, but to cut a long story short, three years, yes three years later, it's as if someone has flipped a switch. I don't know what has done it, I couldn't ever say, she has other birds now and is part of a flock so is not as nervy, she rips up paper and cardboard boxes, she will play with toys at the bottom of her cage, she still can't do foot to mouthwithfood as most parrots do, and the best thing of all is she can fly, she now comes out of her cage, still when she wants to, she will fly round the room, her feet still aren't great but I was told they probably never will be, quite frankly she terrifies me lol, but she is a bird again she flies back in her cage when she has had enough. She is not the he average grey that everyone wants, she can't step up etc etc, but I love her to bits none the less.