you're absolutely 100% right. Honestly I wanted to use a contract for this one but I didn't want to get into an argument with my partners GF about this. It was bad enough that she insisted that she come to the gig and went off on me about an issue with the guys Lavalier mic he was trying to use. The volume was too loud and I was trying to quickly adjust the volume. She yelled at me for what happened. The real problem to begin with is if he wanted to use that mic, at the event he should have let us set things up while we were setting up.
Her excuse for coming with us is she said she was the one who setup the deal for us to do. I have a different feeling why she came.