That may be true, but it does not exonerate her from any wrongdoing. Just because some kids aren't cognizant of what is appropriate or safe to do in certain situations doesn't mean that those things aren't objectively bad or that they shouldn't be discouraged.
She did something that was clearly against school policy and created a dangerous situation. She might not have had the foresight to realize how dumb it was, but that doesn't mean that it was ok to do.
(And believe it or not, the overwhelming majority of students aren't inclined towards harm, and are aware, like everyone else, of the explicit or implicit bounds on what they can do. I've never understood where the perception of kids as oblivious troublemakers with no notion of nor respect for basic social norms and the law.)
To put it simply - she must have been either malicious, irresponsible or dumb. Even considering her age - after all, in just two years she is supposed to be able to legally use cars, firearms and pretty much everything.
That's what being a child is all about. Some people want to see things for themselves.
If I told a younger you about 42.zip, wouldn't you be just a teeny-tiny bit curious about it? Wouldn't you think it would be so funny to email it to a friend of yours at school because of what it did to your machine? What if your school had a zero-tolerance policy for "hacking"?