Because ic is mostly older people starting fresh. Any skill is easier to learn faster when you're young. As I've said twice before, I did the same at 13. I don't expect kids to be amazing, I'm saying it isn't special. Because it isn't.
If she keeps it up but also works on imaginative stuff she'll grow up skilled in more than observational drawing. But she might also not, if she only copies it'll hold her back.
But it really isn't that impressive, most realism artist I've met were at the same level at her age.