Well, we have given it some time and it looks as though our kitty has fully recovered!
The Vet never found the cause to her trouble walking, but he did find low levels of Potassium and Vitamin B, and gave her a vitamin shot on her last visit. He also wondered if the low white blood counts could have been due to an infection of some kind. So he prescribed Marbofloxin to treat the possible infection and Mirtazapine to stimulate her appetite, since she had managed to lose some weight.
Radley is back to her old self, running around and jumping on things. We still are not sure what may have been the cause of her trouble, but we are thankful that she has recovered.