Sarcoptic mange is caused by a mite that is contagious and it can spread to humans and other pets.
Sarcoptic Mange
Demodectic is also caused by mites (ones that are naturally occurring in a dog), but not contagious. It can appear in times of stress (think along the lines of teenage acne in humans - body is going through a lot changes hormonally, growing, etc.). It can also be an indicator of immune system issues. Some breeds are more prone to it at as puppies and once they grow out of it, are never bothered in adult life.
Demodectic Mange
I am glad you had her checked out by the vet and got her on a treatment program. She should be fine once you get the all clear on scrapings, but left untreated it can be some miserable stuff.
Debbie