She is a baby still. What she is doing is very common at this age with GSD, at least in my personal experience.
Had it been me, I would have pulled out some yummy treats, held one in front of her nose and kept moving forward. No reassurance, just, " come on let's go". The bigger deal YOU make of something, the bigger deal she thinks it is. She looks to you for guidance and how to respond.
At the vets, same thing. I would have kept her moving and thinking, not allowed her to focus on the other dogs, as best as possible. Lots of yummy treats to distract her, had her doing "sits" and "watch".
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