This is the stuff that worked--my couch no longer smells like cat pee, hallelujah! It doesn't smell too badly of chemicals, either, which is a nice plus. And that smell will fade, I'm sure. It's Woolite carpet & upholstery cleaner for pet stains/odors + oxygen--some great long name like that.
Minnie continues to improve. There were no pee clumps in the litterbox this morning, which is back to normal for her (Minnie prefers to do her business outside).
Update 12/7: Turns out there was a lot more stinkiness on the carpet around the couch, so I had to shove the whole works to the other side of the room and use one of those spray carpet cleaners on it that you vaccuum up after it sits awhile. NOW the smell is gone!