she could be mad but if it continues I'd place a call to the vet.
Cizzors - my 15 year old cat had to be put down this past year. he started peeing in one spot of the house over and over regardless of what I did to stop it. We now know it was linked to his sickness but didn't know that at the time. It started happening about 6 months before we knew he was sick. (He had cancer, a very fast aggressive type too) You might want to call the vet and get him check out. I wish I had called sooner. Not sure it would have changed anything for us but still I regret letting it go thinking he was just getting old.