I don't know that you should wait until she shows up again with her dog. Some people might get really defensive about it. Assuming she doesn't come over unannounced (or with out warning), tell her before she arrives that her dog peed and pooped on the last visit and that you think its best that the dog doesn't come into the house. If she comes over unannounced, then you're kind of forced to tell her on the spot.

Anonymous wrote:Ugh. Who would seriously think it's fine to bring an animal into someone else's home? Unbelievable.

Um, lots of people. Especially if the homeowner lets them.

Look, the dog is in a new place. there could be a million reasons why he pee'd and pooped: nervous, just bad timing, marking territory, poorly trained.

I'm not sure what telling the owner now will accomplish. Next time she comes over just say, "can we keep Fluffy in the mudroom because he had a couple accidents last time he was here?" TBH we always have baby gates around for when/if people bring their dogs (sometimes announced and sometimes not).