[Yes, she does look like a young Emma Watson. Look out! It's Hermione Granger with a machine gun!]
Now for folks from outside These United States or just uninterested in guns, the weapon being handled here is the civilian, semi-automatic version of the M-16. It can be purchased at pretty much any gun store or gun show for $800 - $2000, in many states, by anyone over age 18 with a drivers license and no criminal record. Yes, "Second Amendment" rhymes with "laissez faire".
Why teach your 11 year old kid to field strip an AR-15? Why not teach her CPR, or carpentry or even poker? (this particular girl may know all these things, but you get the idea) On the other hand, there are plenty of worse things you can get your young girl involved in.
Yes, kids can become fascinated by guns or indeed any esoteric subject- Doctor Who, dinosaurs, dolls, whatever. A lot of kids go through a phase where they love to play cards all day. However, as the father of 3 I know that a child will do most anything to please their parents, even clean their rooms once in while. And kids cannot (legally) learn this much about guns without their parent's blessing.
I am not anti-gun, I own guns and sooner or later I will teach my girls to fire them, if they want. (Since I own high-powered pistols, this will probably not be for a while, since you have to be fairly strong to handle them safely.) Plenty of kids learn to shoot guns younger than 11 but they are usually in a rural environment and usually a light rifle or shotgun for targets or hunting. This is not that kind of gun.
For me, this disturbing image of small girl and large gun she can barely handle brings to mind pictures of child soldiers in Asia and Africa, stoned on various substances, the very embodiment of insane brainwashing and nihilism.

I bet those kids know how to field-strip their guns, too.
If I was going to teach my kids some semi-useful skills, I would teach them this:
Of course that means I would have to learn to scratch DJ first- maybe there's an after-school program in my neighborhood?