Iain, for some reason she's marking the couch -- or expressing her
irritation. Is it new? Maybe she doesn't like the color.
Okay, to discourage your cat, try getting a men's hanky put moth balls (at
least five) in the hanky and the put it on the couch. If it's a big couch,
put out a couple. When you have guests, just tuck the hanky into the creases
for the time being. This will not only discourage the urinating, but will
probably alienate the cat from even sitting/sleeping on it and will do her no
harm.
ElizaBeth Gilligan
Mother of Karma, Intrepid, Jabberwocky and Pyewackett