When people call the cops to complain, they can't do anything unless the complainants swear out legal complaints and are willing to appear in court in support of them. Bitching is not legal action.
If one person is surrounded by 25 people jeering at her, the 25 all say they weren't, and there are no witnesses willing to support the one, the 25 outweigh the one unless there is other evidence.
She didn't have to use her fists to guard a flowerbed from damage that had already been done. A camera documenting the event would have done nicely.
She broke the law because she was frustrated and angry. The court was right about that. The kids apparently are breaking the law, and the community needs to organize and stand up to them legally -- form committees of watchers, post video of the vandalism on the internet with humiliating commentary, petition their local council to up the penalties for vandalism of this park, picket identified offenders' homes -- rather than to call the police and demand that the police do something. That is, if they want to own their own community.