It is good that she is still eating and alert. They go down hill rapidly once they lose interest in food. I've had a couple with Marek's that survived several months with paralysis. One that couldn't walk for about 2 months, did eventually make a significant but not total recovery and although still lame, was able to walk with a limp and fly and resumed free ranging with the flock. Sadly the other got what I believe to be an e coli infection (Marek's makes them prone to secondary infections of that nature) and she had to be euthanized. Good supportive care, good nutrition, sunshine and grass and the company of other chickens (that have already been exposed to the virus) are what I have found help. I don't give up on them as long as they are bright eyes and eating.
Good luck with her.
Good luck with her.