I prefer the model having an escort/chaperone to come along. I’ve been doing model photography for over fifteen years and see that a model that has someone with her is a lot more relaxed before the camera. I have had fathers, big brothers, uncles, and others in past shoots and never had a problem except with one jealous boyfriend. Of course the person attending needs to be supporting the model.
The important thing is any person(s) you bring along should be a positive influence. Besides being there for the model, it is nice for me as I get someone watching my back. I had a Nikon snatched out of my hands on one shoot when I was not paying attention. There are thieves everywhere so it is nice to have an extra person watch the model’s bag and my stuff so we can concentrate on taking images.