The owner of the guns who probably had them under his pillow and in the night-stand drawer should be in jail. That's the source of the guns. That's where they passed from the possession of a law-abiding gun owner to the hands of young criminals.
Charging the girl with homicide seems a bit exaggerated, don't you think. She did what thousands of lawful gun owners do all the time, forget the one in the chamber. That's negligence, not murder.