If this were my dog, I would NOT be taking her to the dog park again until she's been thoroughly straightened out with training. You are risking a lot by doing so. If you feel confident that you can hold her back if she got aggressive then it might be okay if she remained on a leash, but I don't know, I'm just a dog lover, not a trainer. Just my gut feeling.
I have heard lots of good things about the NILF training. Shock collars should be an absolute last resort, just my opinion.
Good luck with your girl
