As long as there is no medical issue going on that requires a vet, she may just be a picky eater. And she also may require a bit less food anyways. Every dog is different.
If you have a piece of chicken/cheese/roast beef.... will she eat that? Cause if she will, welcome to the Wonderful World of a Picky GSD! Not uncommon in our breed and I have one too.
Since I'm on my 2nd picky eater I decided with the first that mealtime isn't a battleground and I don't have to 'Win'. For me, my dogs eating their 2 meals a day is a win, not me picking up their food for a week each time they fail to eat it and just walk away. I don't win if my dogs don't eat.
There are great hints and tips to get our picky eaters more interested in eating their meals so we also can go on with our day --> Pup doesn't want to eat (picky eater?)