Don't let the "puppy" fool you. She can handle a lot more than she lets on. She could be walking on a leash as early as 7 weeks and start training classes anywhere from 8 - 12 weeks. I recommend that she does. That is prime socialization time. GSD's need a lot of socialization to keep them balanced and show you how to be an assertive leader that doesn't need your dog to jump in front of you every time someone wants to say hi. Feel free to email me at email@example.com with any other questions. I am an accredited trainer.
Leash work is good, and so is socialization. But bewware of forced exercise in the first year. This is includes walks, throwing a ball and have them chase it, etc. Forced exercise is not good during this time because the bones need to develop and get strong. Forced exercise could minimize growth and the strength of your dogs bones and muscles. This is especially important in a GSD because they are prone to joint and bone issues due to overbreeding and their size.