You can try to get extra fluids in her.
If you normally feed dry food change to canned as that is about 80% moisture.
You can try mixing the water from a can of tuna with more water to get her to drink extra for the tuna flavor too.
The more fluids you can get her to drink the more she will urinate which should help flush the bladder from infection or crystals.
But if she gets blocked and cannot pass urine then that is an emergency.
You can read about urinary infections here
and one type of bladder stones here
In case you do have an emergency you can ahead of time see if you qualify for Care Credit
A credit card company for health care, including veterinary care.
"With a comprehensive range of plan options, for treatment or procedure fees from $1 to over $25,000, we offer a plan and a low monthly payment to fit comfortably into almost every budget."
They have a zero interest program if you pay within a certain time frame and they list the vets who work with their product.
This site might help
Feline Veterinary Emergency Assistance (FVEAP)
"Seniors, People with disabilities, People who
have lost their job, Good Samaritans who rescue a cat or kitten - any of these folks may need financial assistance to save a beloved companion."
The Feline Veterinary Emergency Assistance Prog ram is a nonprofit 501
(c)(3) organization that provides financial assistance to cat and
kitten guardians who are unable to afford veterinary services to save
their companions when life-threatening illness or injury strikes.
and this site lists more places to check for financial help
Hope this helps you!