How can this person not be charged with anything?

The police can only arrest you for a crime. It is up to the state atty to file the charge. I know it sounds crazy but it happens all the time. The state atty has to think ahead to see if a judge or jury would actually find the person guilty. In this case if the atty thought the woman would get a sympathetic jury or judge they would drop the charges. The worst part of our legal system is that someone can commit a crime and get off cause the jury would say that they would do the same in that situation...

There is obviously some circumstance with this ladies mental being that is on record. If not , the law is usually quick to file charges for obstruction of justice or reporting a false complaint.

At least in the state of Florida, charges like this can only be filed by the state's attourneys office. If the state attourney does not think that the charges are worth the time, then they do have the option to not file charges, and it is at their discretion.

the police are usually nice people. they dont want to charge someone for being an idiot. if it happens again then there will be a problem.

pretty much a get out of jail free card. they have lots of them and hand them out frequently. sometimes they hand them out to the wrong people though

she's probably a known mental case and it would not go to trial.