
I'm not into GSDs specifically, but in general, with medium to large breeds, my main breed included, the frame is there by around 7 months, but it can take quite while yet, for them to fully body up - especially the males. I had a boy who I started showing at around 6 months but at a time when it was all about big, heavy, I soon felt I was wasting my time with him and withdrew him until he was close on 2 years before trying again.
Actually the slow maturing lines often do far better eventually, provided they are generally healthy, to take their time maturing.
You might talk to her breeder who should know how his/her line develops. Has she been wormed? I'd stay away from high protein food too - all too often that forces too much growth, too fast. Again, not necessary.