Oh, oh....I really don't know what I'd do except if you think separating them will work.... How "cat friendly" are your guests? If they are fellow cat lovers, they will understand and may even offer some good suggestions and a few more pairs of eyes to watch and see what's really going on. If they only cat tolerant though, separate - definitely. However, I can't imagine anyone only "cat tolerant" visiting you. Is the Yorkie familiar with cats? How familiar are the cats with Yorkies? I can only see the Yorkie adding to the problem, but you never know. Maybe like Eddie and Edwina they'll join forces against the D-O-G and forget their own animosity for awhile.....hopefully.....

All I know about cats peeing right in front of me is when Peanut did it, it turned out she had a tumor and had to have surgery, so if it were me, I'd panic and have Leila at the vet so fast her head would be spinning! Hopefully this is not really the case with Leila.