I'm confused now. So she wasn't attacked, but she's fearful of other dogs who nip at her, including older dogs who find her annoying, and you want her to nip back? ("Usually its old dogs who just want to mind their own and mine tries to play with them.") As opposed to de-escalating, which is what she's doing now?
If an older dog thinks she's being a pest and growls at her to tell her to go away, what is your reasoning for expecting her to "fight back"? As an owner of a senior dog, if my younger dogs bother him, they get told to leave him alone -- by me. I'd shoo a pestie-youngster away from him at the dog park, if she were jumping on or nipping at my old guy; and as an owner of a young dog, I'd get my youngster away from any one else's senior she was bothering, as it's not acceptable behavior to me, and seniors should be able to enjoy the park without young ones harassing them.
She's an insecure dog. I have had several dogs like that--we paid for a lot of sessions of controlled play care where all the dogs are carefully screened and matched to play style (my little adolescent GSD mix currently gets matched at the vet's play care with little dogs, as the staff there understands the play care is rehabilitative for her, and they won't overwhelm her since she's a very gentle playmate--the rough-and-tumble of the big-dog play time would scare her--but she made friends with some of the little dogs). With my shy ones, I take it slowly and let them decide when they are ready to run and play.
It sounds like from your first post that she's telling you with her body language and avoidance that it's too much for her.
Last edited by Magwart; 12-30-2012 at 12:03 AM.