Older cats are more prone to develop conditions like diabetes, kidney failure, liver disease, and hyperthyroidism, and her symptoms may be indicative of these, and so many other underlying medical problems; however, her pale gums are of the most concern, as this indicates anemia and/or internal bleeding. If she is also experiencing labored breathing, her pupils are not responding to light as they used to, and she's shaky when she walks, she may have suffered a stroke.
Start dropper feeding her if she won't eat or drink on her own. This method will be easier than using a teaspoon. Get a 1cc sized dropper, or a medicine syringe made for pets or children, and water down plain canned cat food and/or plain jarred baby food chicken with NO onion products (Beechnut Stage 1 chicken and chicken broth is a good one); give her 1cc every 15 minutes for an hour, then repeat in 2 hours, if she's still not eating on her own. She's also probably dehydrated, so dropper feed her plain water or children's clear, unflavored Pedialyte on the same schedule, just alternate with the food, but let her rest in between. Gently go in from the side of her mouth, where there is an opening between her upper and lower teeth. Squeeze in a little bit at a time and wait for a swallow; you can gently stroke her throat to encourage the swallow reflex.
Considering all the symptoms you described, it would be best to have her evaluated and treated as soon as possible, so if you have an ER vet center in your area, bring her there, now. If not, you'll have to wait until tomorrow, to see your regular vet.
I hope all will be well with your furry girl, once you have her diagnosed and treated.