She varies her target areas from the hall floor to the back of the sofa, occasionally the living room carpet (which at least has the merit of being easy to clean up with the carpet washer) or, and this is the most obnoxious, the kitchen floor within a paws reach of her food and the cat flap. There have been a couple of changes but she's been peeing unsociably for ages before I moved the bookcases.
She does it most in bad weather, she doesn't like going out into the rain, and when it was snowy, we literally had to post her out through the flap.