Cat pees in one location and it's not the litterbox

Hi,

Our household has four cats. One cat, Lilah, has been peeing on the same couch over and over again. My wife is at her wit's end and demands that Lilah remain supervised or locked in my office.
Lilah never peed outside of the litterbox before I got married and moved in with my wife. Lilah doesn't pee frequently on the back couch, just once every few months, and I believe she's calming down with the bad behavior. The rest of the time she uses the litterbox in my office and I go out of my way to praise her for taking a proper whiz. Rarely Lilah will leave a spot on the rug which I try to clean up ASAP and to the best of my ability.
What can I do to ensure Lilah is happy, not a prisoner and doesn't piss on the gosh darned couch? We have lots of other furniture but she doesn't touch them even though she lounges and naps on them.

My first suggestion is to take the cat to a licensed veterinarian to rule out any medical issue. Assuming the cat has no medical issues then I have some behavior suggestions. But first make sure all the area's the cat has urinated on inappropriately are thoroughly cleaned with an enzymatic cleaner. Then simply deny the cat access to the area where she inappropriately urinated for a few weeks. Plus keep her confined to one room for a week or so that way she gets used to using the litter box again. You could also try using cat attract litter for a few weeks as well.