I COMPLETELY agree with Dixie. . my advice, is to not take an aggressive dog to the dog park. Honestly, it sounds like you've spent a lot of time/money training her, and you are responsible about it, but Dog Parks just are not for every dog! Dogs who are that posessive, dominant, and don't inhibit their bites (which is what it sounds like) do not belong with other strange dogs. I agree, totally, that you shouldn't have been playing ball with other dogs everywhere if she's that aggressive about it. And, if you know she doesn't like Goldendoodles, or that she would've attacked the Goldendoodle if it stole her ball, you should've left the park before this happened. Is there another fenced/off-leash park that you could exercise her and find a time or area where there aren't other dogs around? It sounds like that would be best for her. At our local dog park, there is two sections : one big side for outgoing, big dogs, and one side for shy or small dogs. The small dog side is usually empty, and people with less social dogs are able to exercise there dogs there, usually alone. Maybe you could find a park with that kind of set up?

From my experience, I would've been angry too if I was the Goldendoodles owner. In february, my dog was attacked by a VERY dominant female Rottie, her behavior sounds a lot like your dogs behavior. She was very possessive, trying to dominate all of the dogs there, and my dog literally did nothing to set her off. She pinned him down and bit him, even though he was clearly on his back and yelping and did not challenge her, then when he was able to run off she chased him down again. Her owner, unlike you, thought there was nothing wrong with that and hardly even came to get his dog. I know I was really, really angry and it generally ruined the dog park for me! I no longer want my dog to associate with dogs/owners I don't know, after 3 years of him never even coming close to a fight, this one experience ruined the dog park for me. He had several punctures on his chest and neck and his mouth was torn up, which cost $100 at the vet and took a month to heal. Put your self in other owners' shoes. . . would YOU be angry if a dog randomly attacked your dog at a dog park, where you expect only friendly dogs to be? The rules of the dog park, I think the #1 rule is, NO agressive dogs. I understand that you have worked a ton with your dog, but that could definitely be her personality in general, training or no training. Some dogs are just 'Alpha', and don't do very well at dog parks, where there are plenty of unruly, hyper, playful, ball-chasing dogs that could easily aggrivate them.