She could have protected the dog and saved her job simply by breaking the guys car windows.
If she saw this man put the dog in, why didn’t she ask him if he would be out soon or hope he doesn’t leave the dog long, right then?
Immediately calling authorities - tattling - is a good way to piss off people right away. In any case, you can watch the dog, or if you know the person say something first, or find someone to do so. Not good form to bring in the big guns right away. Be brave and talk to the person first, give them a chance to correct themselves rather than giving them a record. This is not a robbery.
Not to say that she had to be fired, or that her intentions weren’t good.