I'll bet you have only heard part of the story so far.
I wonder what she said at the time and to the police.
The article makes the case that she was arrested for pointing a finger. I suspect that she was arrested for something else.
I can see a cockeyed school administration making a bigger deal than necessary over a finger point but it is much less probable that a police department would and nearly unbelievable that a District Attorney's office would. Most DAs are elected officials and would not want to explain this to the voters before the next election.