Dog growls towards other dogs

So I have a pit bull lab mix who was a rescue dog from an abusive family. She is now 8 years old. She was adopted by a friend 4 years ago but I recently adopted her in February because of a divorce. Anyways, she is the sweetest and most playful dog, however when I go to the dog park she likes to growl.

I used to see her chase after dogs and have fun. I've seen 3 Chihuahuas chase after her. She used to be fine at the parks. Recently she went to the park there was a killer pitbull bully there. Within 3 seconds at the park this dog grabbed my dogs snout and started ripping. She cried and was pouring blood. Since then, she growls at almost any dog and I think it provokes fighting. When going to the park I give her a ball in her mouth so she can not bite. But this last week she got in another fight and got hurt again. Both times it wasn't her fault, it was aggressive dogs that immediately fought. But, she still has this growling problem which I've seen it upset other dogs so I often leave before something happens. Can I train her to not growl and play nice? As of now I'm not going to take her to parks anymore until I know she can be safe.

Dog growls towards other dogs