Anoni Mus said:
Justified? yes. 100%? No
She knew they had a knife, she had a shotgun (seriously, I mostly disapprove gun ownership, but can understand it, but not Shotgungs, why would anyone need a gun for self defence stronger than a simple 9mm?). She could have just pointed it and hope they leave, and just if they still advanced, shot them. Or she could try to shot in a non fatal area, like legs or arms.
Just read the comments on the OP link. Those are scary. Some of them say they should all be exterminated, wtf...
She was locked in the bathroom There was no reason for them to come into the bathroom unless they were planning to harm her. I mean, what, you think they needed to take a shit? Clearly a case of self defense.
As for your sidebar about shotguns, shotguns are a fuck-ton cheaper and easier to get than handguns. Several states actually outlaw handgun ownership, meaning you can't get your hands on a simple 9mm. For reference, the 870 express remington shotgun is one of the best shotguns out there, and it costs less than $300. For an automatic short barreled 9mm, which is about as cheap a handgun as you can get, you're looking at about the same price. The handgun I'm planning to buy is closer to $1000 And you need to get a pistol permit, which take a long time to get, 6-8 weeks if your lucky, and usually has some pretty stringent requirements attached to it, like being 21. The girl was too young to own a handgun in most states.
Second: a 9mm is not an adequate weapon for most people to defend themselves with. Handguns are hard to shoot, they take hundreds and hundreds, if not thousands of round fired at the practice range to gain the proficiency needed to hit the chest of a man if he's standing still. To hit a moving target reliably with a handgun is a very rare skill.
Also, 9mm handgun rounds have a very low stopping power. It takes 3 or 4 or even more hits to stop someone before they can hurt you. It's not like the movies, you don't shoot them once and they instantly die. A person who is shot once with a handgun is going to be alive for several minutes, and conscious for a significant portion of that. Even the .357 magnum, the most powerful handgun available, isn't a guaranteed stop with one shot. Self defense training teaches you to keep shooting until they hit the floor.
As for hitting a non-vital area, a 12 guage shotgun would pretty much blow off a limb even if she managed to hit such a rapidly moving and small target. This means there really isn't any non-lethal area to hit with a shotgun, he's gonna bleed out no matter where you hit him. And shooting someone in the arm isn't going to stop them from attacking you, which is the whole point of self-defense. Hitting them in the leg would, but unfortunately, the legs are pretty much the hardest part of a person to hit. They're small and they move very rapidly and often unpredictably. There's a reason that even police, who are required to practice, are trained not to aim at the legs, it's pretty much impossible to hit them well enough to stop them.