The normal breeding season for cats is between spring and late summer. She will likely go into heat during this time of year. Decide if your cat’s in heat or sick. If she’s acting restless, but not rubbing herself against everything and lifting her tail to the side, she may be in pain. Take her to the vet to find out what’s going on.
If you have a male cat in the same house, find a friend or hire a cat sitter to take him in for a couple weeks. If the two cats stay in the same area, they’ll both act wild, and almost certainly end up mating. If male cats are visible through a window, cover the window with curtains or a piece of cardboard.
Note that this is only a temporary fix, but it might buy you an hour or two of peace.
Follow the instructions on the labels. They may tell you to add the remedy to the cat’s water, rub a few drops into the cat’s fur, or use as an air freshener. Do not use products intended for humans, which likely use higher dosages.
Don’t use cleaning products with ammonia. Ammonia is also found naturally in urine, and the smell will encourage her to mark that spot again.
If you can’t afford the surgery, look for low-cost spay services. Many clinics offer this service at a reduced price because it reduces the population of stray cats. Look up your area in the databases listed on the USDA website. There is a small chance of leftover ovarian tissue sending the cat into heat even after the surgery. If this occurs, consult a veterinarian.