Cops are (rightly) held to higher standards than 12 year old girls alone in their home with an intruder.
In principle.
Fair point.
If you keep a gun for protection you should be practicing shooting monthly at the least. You should mark out your firring positions and know what is behind them. If you do these things an attacker has little chance. They will be in an unknown place facing unknown forces. And don't hide. Hiding moves you to a crappy position, make the other guy try to hide. Lastly, don't show your gun or threaten them with it. It is for killing, not tough talk. If you need the gun, yell surprise!! and don't stop shooting until the attacker is done for.
All well and good, from your (surely greater than 12) years of experience, but this was a scared little kid. Put yourself in her shoes. I think we should just be happy she knew where the gun was and how to use it without hurting herself.