Well ... you're at a crossroads here. As I view it ... the way people end up with problems is when they take the "my other dog road was like...."
"This" is not your other dogs ... this is "This dog" and she has said ... "I am uncomfortable around unknown dogs."
I would "respect" her choice and make adjustments with "This" dog in "My Approach." Dogs don't have thumbs they can't send a memo as it were ... note to owner, "I am uncomfortable with this approach ... please stop ... signed Foo Foo."
Work with the dog in front of you, you're fighting a battle you don't have to have here.
Couple of articles are in here, "Why Dog Parks are a Bad Idea" and "Three Dogs Who should not be at a Dog Park" :
I would stop putting pressure on her with the other dogs stuff. And I would start doing this:
Fearful, Anxious or Flat Crazy "The Place CommanD - Boxer Forum : Boxer Breed Dog Forums
The goal ultimately would be a two hour "Place" with distractions. At some point you can start to do "Place and Sit on the Dog" with "Distractions" outside the Dog Park ... no contact with unknow dogs. It will give your dog to "time" to adjust, and show her that she can "trust you"
...not to put her into, for her "uncomfortable situations." Ultimately ... she will be who she will be??? But you will not be "forcing the issue"which may or may not "break her??"
But .... true confession I don't do "Dog Parks" in any case, so it's not a problem I've ever had?? And my dogs do just fine around other dogs ... most likely because ... they have never had a "Bad Experience with other dogs??
But if you don't like my approach go with "MAWL" socializing with other dogs is more her thing.
I just say "NO" to unknown dogs myself, as I like to employ the "KISS" principle ... works out fine.