If you don't know then you should get another vet! If it is sarcoptic don't go because you can spread it, if it is demodectic and around the eyes and the dog is a pup then 90% of the time will resolve without treatment . Best of luck!
Demodex isn't transmissable like sarcoptic. All dogs have some demodex on their skin - the dogs that have challenges to their immune system are the ones that have a hard time keeping the normal numbers under control and they get the outbreaks. So could be shown if the hair grows back in time - can't imagine it will in time for the show is the only thing. If you have already entered her and are going to go to the show regardless even to just watch the dogs then take her with you. Never know might look fine by then.