Is your cat neutered?

Having suffered from this problem for many years in the past, I quickly discovered that if one inhibits spraying in one place, a cat will just find a new place. A cat who decides to spray is nearly impossible to stop. I tried various medications etc - nothing worked. And yes, the last cat lived to be 18. At that time, much as I love cats, I decided no more kitties - just couldn't take the chance.

Anglo is right. You can't stop a cat. I'd find something to put in the corner that she could spray on that could easily be washed. Her next spot might be worse!

Also, if you haven't, see if the vet has advice, especially if it's a new behavior or if she's not spayed.