in my opinion, as long as your dog was undercontrol, you warned the other owner that your dog is aggressive & the other dog is loose, you are in the right!

I don't know how many times I took Max & Rocky (at this time he was kinda agressive but not doing the killing everything in sight) to the park & my exfriend & I stood in the tennis court's door way & tossed a ball to the dogs. They had a blast & Rocky was not muzzled so he could play with Max & the ball (he wouldn't hurt max he looked up to Max & if Max was angry he was angrier!, if Max was happy he was happier, hehe ) Rocky also would never leave our side nor Max's side. SO he was under control. Sure he barked at few times at dogs, but when we told him to stop & he looked at Max, he would stop & get back to playing, as Max never barked at dogs & he was a big baby hehe...

I say, bring her back to that park, but bring a friend with you, so you both can stand in the gateway. Cont to keep a muzzle on her & do keep her behind you. When Max was young I noticed that he was FAR more protective (anything at moved or looked like a trash can he would get agressive, but if I forced him behind me, he seemed to relax a bit, not 100%, but enough that I could atleast walk. After the years, he turned into a new dog & he loved & like everything, EXCEPT trash cans at night