If her primary concern is nightmares and flashbacks, she needs therapy, not a service dog. Therapy will attempt to solve the symptoms, atleast lessen them significantly and give her coping strategies to continue lessening symptoms over the years. A service dog is nice... a dog is nice, period, doesn't need to be a service dog. They're calming and often pretty good and recognising emotional disturbances in people, thus they will cuddle more or less with their owner as a result.