Personally I wouldn't trust someone who has never done them before. I mean I don't know what a "professional" babysitter's training entails, but in my experience people who have never done psychedelics tend to accidentally do arbitrary things that set off a bad trip at a much higher rate than those who have done psychedelics. People who have done them before tend to be able to see how things might lead to a bad trip.
I solved a bad trip one time by turning the TV off in the other room. It was almost inaudible to me, but it was playing WWE and it was just... negative. Turned it off and everything was fine, but the other babysitter (someone who'd never done psychedelics) couldn't be convinced that the TV was the issue because they couldn't see how negativity could cause a bad trip.
This is all probably just bias on my part. No reason a professional psychologist couldn't make these connections too.