You should step in and not allow the other dogs to dominate her. Are you doing any formal training classes with her? I'd get her involved in something so her confidence grows.
It isn't fair for her to feel intimidated by dogs, especially if they gang up on her.
Maybe a one on one play session with a dog she really likes would be better?
Is she spayed?
What Jane said. Particularly the part about obedience training to give her confidence, agility is great for this and female shepherds are usually gifted at the sport. She'll be around other dogs in a controlled environment and if you're lucky, get a good trainer who can pick up on her subtle behavior clues that make other dogs want to dominate her.
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