a good trainer should be happy/should understand you wanting to go & observe a class first before you decide whether it's right for you & your dog so if i were you i would ask if i can watch a class first & make sure your happy with everything

Ask to go along and observe a class without your dog first... If she won't let you 'warning bells' should sound... I once went to look at a class near me that on paper seemed perfect for dealing with Kismet's issues, but on watching them, they used far too many aversives for me... check collars, rattle bottles, even CM 'rolling' and Jabbing... I thanked them for letting me come along and said we'd get in touch.. then ran for the hills!

In addition to observing a class and the methods, I'd take a good look at the environment. For example, a class held in a large room wouldn't work for me at this point.My dog would start out super excited. Barriers are important too. Something that is important to me would be to have at least one private session with the trainer. Not all reactive dogs are ready for reactivity classes. Mine was not. I needed to do some groundwork first.