A dog park is not the place you want to take her. If you want her to interact with other dogs I would suggest doing so with dogs and owners that you know, in a controlled enviroment.

I am torn between telling her "NO" and cooing to try and calm her down. What should I be doing?
When she shows this behavior please do not baby her, this will only reinforce the behavior. I highly suggest contacting a behaviorist in your area (your vet can give you contacts). They should be able to give you advice.