People are pretty hard to draw, and drawing skill depends on quite a lot of factors including how much you actually want to draw the subject (and how tired you are, whether the pen or pencil is the right size for your hand which many are not for childrens hands).
Proportions aren't bad - subject has shoulders which many kids forget about, facial features are a/in roughly the right places and b/express character/emotion, so those are all good things.
Something to look for (but I would not set her up to test it as likely you'll put her off drawing)...
Is she drawing what she knows is there, but cannot actually be seen/fully seen in real life?
For example the pony tail on the side of her drawings head - is it really on the side, or, knowing there IS a pony-tail there, but it's not visible from a front view, she's put it on the side even though you can't actually see it in real life.
Thats usually a big step in drawing skill... not drawing the things we know are there, but actually can't be seen. For example the legs you can't see on a chair because the other legs block the view - inexperienced/young artists will put them in because logically, a chair has four legs, they know this, thus they must depict it... it feels wrong not to.
I'd also look at pen/tool control - can she colour in the lines basically. If she can't, at 8, that suggests she struggles to control the tool so a hand/eye co-ordination issue (but again could be affected by unsuitable tool, unsuitable paper, and just not caring!)