I don't think this article provided us with enough information. What were the kids doing when she attacked them? Were they just random kids that she'd never seen commit any crime? If so, she's psychotic. Were they laughing and looking smug about what their buddy had just done to the flower beds? If so, I'd say that she has anger management issues but that she didn't deserve a full sentence. Were they kids she'd
seen vandalize before, laughing and looking smug? If so, she still over-reacted, but again, she shouldn't get twelve months in prison for it. Were they kids she'd seen commit vandalism (and could prove it)? If so, she's mostly justified (though throwing the bike was a little "out there").
I hear "vigilantism" bandied about a lot, and I'd like to propose a question: What is vigilantism, and what is bad about it?
In my mind, vigilantism is people upholding the laws when the police refuse to uphold them.
BZZZZ. FULL STOP. HALT. 
That is IT. That is the LIMIT of what I believe acceptable. I do not believe in the anarchy that most people think is the result of vigilantism. I feel obliged to get your attention because otherwise that is the inevitable argument used against me, even though
that has nothing to do with what I believe.
If someone upholds the law in an orderly manner, they should get a medal. If they uphold the law in a
disorderly manner but no one gets hurt, they should get reprimanded and maybe do additional community service, but no more. If someone upholds the law in a disorderly manner and there is damage to life or property, they should be held accountable, but maybe with a somewhat reduced sentence, depending on circumstances. If someone carries out a
personal agenda in the name of upholding the law, or if vigilantes bring the wrong person to justice, they should bear the full wrath of the law. No more, no less.
Doing this "upholding of the law" is only acceptable
when the police refuse to do anything. That is acceptable. More is not.