Just like anyone of us animals grow old and need to have special care. Your beloved and once playful kitten may have come to a stage where she needs special attention. Generally cats older than seven years are categorized as geriatrics by veterinarians.
Make sure she is active and maintains healthy weight. You should barely be able to feel her ribs. If she is heavier cut down on her food and add more playtime. If you feel she is too thin increase the amount of food and if she fails to gain weight take her to the veterinarian to determine if there is an underlying health problem.
Give a good quality cat food. Avoid giving human food as this will have too much salt and fat for a cat and could lead to heart disease, diabetes and liver failure which they will become more susceptible to as they get older. A cat this age needs to be checked by a veterinarian at least twice year to determine their general health.
You need to look in to the oral health of the cat as tooth decay is very progressive and leads to various infections. Make sure to brush her teeth often.