It could be, I would keep a close eye on her. One lady at my job ended up in
a hospital with a severly lacerated leg after her cat suddenly attacked her
during the night. the cat had some kind of dementia and thought she was an
attacker.

My suggestion would be to get her to the vet asap! If your cat is 18...she
may be close to her time. Cat's arn't very good communicators when it comes
to being in pain or being ill. They don't always tell you. If you have never
seen this behaviour...I would be consulting with a vet to see if she has any
underlying health problems. With cat's it's impossible to tell. My father
had a cat that had had kittens. He had sectioned off a room by placing a
board across the doorway. For a week the mother cat would jump over the
board to go outside. One day when my father came home...the cat was lying on
the floor panting and not moving. After going to the vet they discovered
that the cat had been hit by a car and had suffered serious internal
injuries. They somehow summized that the cat had been hit shortly after
having the kittens...but she never showed any sign of pain...she kept
jumping over that board and looking after her kittens until she just
couldn't do it and finally collapsed. Just to show...you just never know
what your cat could be going through.
Good luck...I hope it's nothing serious.
Melanie

My parents have a cat that is at least 22, since it has been 22 years since
they took him in as a stray.  He is half blind and has survived cancer, but
he still has a good quality of life.  His vet is astounded that he is still
alive when they take him in every 6 months.  He has traveled the country,
gone fishing, and entertained guests all that time.  He has kept my parents
company through their illnesses, and always been there, purring and doing
his job as bed warmer.  He has gotten crabby in his old age, and he
sometimes howls at night.  You are right, they get lost and confused.  My
parents just scoop him up and pet him and he is ok.  They keep wondering if
he is still enjoying life, and I tell them that they will know when he
isn't.  Right now, he still eats, sits on the front porch, and cuddles.
When he stops doing those things, I think it will be time to let him go, if
nature doesn't take him first.  I recently lost a cat just short of her 13th
birthday.  I was there when she was born and she died in my arms.  I hope
you treasure each day with the old girl, because not having her will be very
unpleasant.  Just reassure her when she is lost and confused, love her, and
she will be ok.