Maybe she did it because she was terrified of dogs? It's actually pretty common and I doubt she crawled up your wife's back because your Pekingese came up to her. That said, unless the saleslady was there at your invitation (meaning it wasn't a cold call) she should be in a different line of work.
Of course she was terrified. But dogs are not uncommon and thus should be expected at homes. Her inability to act rationally around dogs should have precipitated an opening statement from her such as, "Do you have a dog?" and if so "I'm sorry but I have a phobia, would it be alright to put the dog somewhere else?"
In inviting people to my home, I expect them to act rationally and to warn me if there are situations where they cannot act rationally.