Hmmm...I know of no controversy about supplementing with methylcobalamin and many members do. I use it in my CKD kitty. I wouldn't just get any methylcobalamin. Here's the one most in LL use:
Zobaline
Does Cleo have chronic kidney disease? Did you check all of her tests just to make sure she doesn't run a little lower? Here's some good info about potassium levels in cats:
Potassium. While this website is considered to be the bible for CKD, it also has some great, basic info. A stilted gait in the front legs can be due to a low potassium level.
Please keep us posted.