Please take her to the vet and tell the vet what she is doing. Peeing outside the litter box is the
#1 symptom of urinary tract problems!
If the vet says she is okay, then consider making a few changes.
If you use a covered litter box, take off the lid. Many cats refuse to use covered boxes.
Cats prefer fine grained unscented litter. So, you might try changing litter.
Make sure you have at least one litter box per cat (if you have more than one).
Make sure you scoop the litter box daily, and with multiple cats, scoop twice daily. Cats often refuse to use dirty boxes.
If your litter boxes are real old, they may have absorbed odors even if you regularly clean them.
So, try buying new boxes.
Make sure your litter boxes are in a place where the cat feels safe while going potty. If she is disturbed by you or your kids(?) or any other animals in the house while she is trying to potty, she will choose to use a safer location. So, move the litter box to a location where she can see the comings and goings of the other people & animals in the house.
Put a litter box on each level (floor) of the house.
Make sure you thoroughly clean all old urine spots on the rug and elsewhere. If she can smell the old urine she will think that place is a good place to pee. Use a flourescent black light to find old urine and treat all old spots with an enzymatic cleanser.
Try putting a plastic carpet runner upside down on the places she likes to pee....most cats don't like to walk on the "spikes" so they will avoid the covered spots.
Hmmmm. I'm sure there are other suggestions to try.
If all else fails, your vet can prescribe psychotropic medications that reduce inappropriate
peeing, but try these simple solutions first so that you don't have to give her pills the rest of her life!