I don't know if you have any kind of sole-agency or how it works in your neck of the woods... if you can...
Play a little game with the stinker. After the showing tomorrow tell him his "services" will no longer be required. When he asks why you tell him his little dirty underhanded tricks of running around behind your back and whining to X are not acceptable. You do not do business with backstabbers.
Let him apologize and warn him that if he EVER communicates with her behind your back again he can kiss his commission goodbye because that is a breach of contract in your books.
Let the SOB sweat a bit.
Gardener, I really like Gnosis' approach here. One question for you: Who does hte listing agreement say the realtor represents? If it's just you, he has likely breached the agreement by having a confidential communication (one he should only have with you) with your X. Probably some state ethical guideline he broke.
Just saying. Might be worth asking him about. And if it gives you a basis to can this guy, get another realtor.
