First and foremost, I'd shut off any rooms where the cat isn't allowed. So many times people try to humanize their animals and this causes problems. (I'm not saying that she's doing this but once a habit is begun, such as allowing pets to sleep w/their humans, it's difficult to break.)

After a cat has soiled an area, clean it w/an enzyme product such as Urine Gone and completely saturate the area w/it to remove all traces of odor. If you see the cat going near a previously soiled spot, in a firm, loud voice (don't shout), say "NO!" and shoo him/her away w/a squirt gun.

If all else fails, your vet can give you a prescription for Clomicalm. A few of my cats are on it and it's worked wonders. I haven't had an episode in months. Some PTers have had more success, however, w/Prozac, either a patch or pill. I wish I didn't have to medicate my cats but it's better than the alternative. Houses and furniture are expensive and, more importantly, our environment should be clean and healthy, not reeking of urine and feces.

Good luck w/this. I know how difficult it can be. If none of these suggestions work for you, then probably rehoming would be best, as long as you rehome them together. Please don't put them outdoors, though. Too much can happen to an outdoor cat. The average life span is only 2 years versus 17 1/2 years for an indoor cat. Hope this helps.