At the point that the woman jumped on my wife's chest, our dog went nuts, but did not bite here because I was right there.
In my opinion, the saleswoman showed extremely bad judgment and created a dangerous situation.
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.