The Stars and the Cookie Jar

Only your vet knows for sure. Vets being expensive and stuff, there's always the animal shelf at your local Major Chain Bookstore With The Most Comfortable Chairs. They might have something out about aging cats. I know I had "Your Aging Cat" around here somewhere from the bargain bin, but can't lay hands on it at the moment.

My understanding is that as long as they're emptying the food bowl, filling the litter box and maintaining their weight (weight loss is not a good sign in kitties) they're usually doing well. I've never heard much about kitty mental health, since everyone seems to assume they're all whackjobs on the make to begin with.

if she bit you, and if she's licking nothing, it might have something to do with her gums, or otherwise sore mouth. Our Beanie lost a tooth to gum disease, at an advanced age-- so did our male, Sledtracks, when he was fairly elderly. Things like blocked saliva glands, etc.

there are such things as cat dementia, but more often I think there's a medical reason for weird animal behaviour. We've had LOTS of cats and never had mental problems to deal with, other than just the intrinsic (but consistent) weirdness of each one. When they suddenly change something that specific, it's usually medical.