At least the dog will find another home...

Personally, I can tell you right off the bat that I never ever ever let anybody unfamiliar step over my dogs. At our office, some people bring their dogs and they will lay on the ground. I will never step over their dogs without asking. Stepping over a sleeping/laying dog is extremely threatening. I'm sorry your grandfather got bitten, but it sounds like there was severe and constant miscommunication between dog and humans.

Obviously, I love Dobermans with a fierce passion, but at least this girl will find another home where there is clearer communication and leadership.