Calling a pet a service animal should be a crime. If the woman and her husband are not blind or otherwise disabled the dog should not be allowed on the plane.
Perfectly normal looking Veterans with Posttraumatic stress disorder (PTSD what in my day they called Shell Shock ) use service dogs. Does that fit your definition??
Some service dogs detect seizures in their owners.
Service dogs have training, so I think having proof of training should be the requirement.