Thank you, Sourwolf.

You hit the nail on the head.
Huh. No matter, though, really. When I told DH about sis's self-invite he laughed so hard that he choked on the burrito he was eating. I should have chosen a better time to tell him.
That issue is actually moot, though - there was really no chance that they would be coming to stay - the OP was really about how I could have made their last visit less of a disaster. That last comment was a little tongue-in-cheek because I thought it was really funny that she would contact me about staying again after what happened last time.
Yeah .... that visit is not going to happen in this or any other universe. AT LEAST AS FAR AS WE ARE CONCERNED. But convincing SIS of that may be a different story. I really had intended to give her the excuse of emergency dental surgery but DH says not to respond at all.
I'm glad I ran it by you guys, though, because the advice you gave about making sure they KNOW they are not welcome is good advice, so I'm going to have to make sure of that today. I did say last night that I better call her today and make sure she knows not to come.
I'm just dreading that phone call. I better get to it.

I'm just trying to think of the least drama-free way of making this visit not happen. Maybe the "you do remember we live in this apartment....right?" is a good one. Not personal. She takes everything
very personally.