How to deal with a negative next door vendor. Advice needed.

I did a show yesterday and I was placed next to a vendor who had nothing but negative comments all day long. Granted, it was a slow day and nobody did as well as hoped, but she went way beyond the typical comments. I first spoke to her when we were still in the parking lot. Check in was to start at 7:30; it was then about 7:15. I went to her car and asked if she knew where to check in, if she had done this show before, etc. She immediately came back with “this better not be a rinky dink show”, “I only do high end shows with xxx and xxx”, and “I better make some good money”. Ok, so I step back and go find checkin. The gentleman running the show was kind and friendly and told me…. Guess who I am next too! Ok, make the best of it and move on. But because it was a slow turn out, she ended up standing at my table a good part of the time with nothing but negative comments.. about the organizer (his wife had run the show for years and she just passed away. he decided to go ahead with it in her honor and because the church was very supportive of him); nasty comments about other vendors and their products; comments about the customers if they walked past and did not buy. And when her friends stopped to say hi, the three of them stood in front of my table yakking, so customers could not see one whole section. Any advice in case this happens again? I just tried to always be busy when I saw her coming close.