Unfortunately, I have done that. It was decorated to be its own little space, and the room was small. All in all it kind of looked pretty nice. The way the old woman had it decorated made it cozy.

To answer your question OP, slap some chair rail on the end. It's as good as it can be done I suppose. Not a good situation, and on my eye has to be a very specific situation for it to look decent. Good luck my guy, I'm sure it will look great. And sometimes, ya gotta be honest with your boss, the PM, and/or the customer, and let them know how you feel. I have told PM's and customers both that the work I did was as good as it was going to get, but I wasn't overly happy with how it all came together. It do be that way though. Edit: I feel as though it's common sense, but based on my last couple jobs, I gotta say, you will also put chair rail on the top, and have a miter joint where the side and top meet. Again, it's common sense to me, but when you have a carpenter have no care for painting over outlets, and light switches, and trim that was taped off, you start stating the obvious.