I'm sorry about your sweet hen. Since she was vaccinated for Mareks, and she is 2 months shy of 2 years old, I would wonder if she hasn't severely injured her leg that might have caused nerve damage. Of course Mareks vaccines are sometimes omitted accidentally at the hatchery, and can even fail. I know that doesn't help, but it you can afford it, you could get her tested with a PCR blood test with blood drawn by your vet, and sent off to a poultry lab such as Texas A&M. Necropsy and Mareks testing can be done by your state vet if she dies. It might not help, but you could try some poultry vitamins that include riboflavin (vitamin B2) just in case it could be a vitamin deficiency called curled toe paralysis. Let us know what happens.