I can't say anything technical because I don't know anything about digital art. Anything that inspires you to do work like this is a good thing. There is no doubt that this is a real person. You have captured the spark, regardless of the medium.
It's fine the way it is, but there is one thing you can think about. Her lips are fully outlined, and I don't think this quite fits. The shape of her nose is indicated, and the details of her eyes are indicated. The viewer's mind fills in details on these. The level of detail that is really there and the level of detail that is indicated are the same for the nose and eyes, but not the mouth. You could do something less to the mouth to make it match.
That's one of the hardest things, I think. Making the veiwer see more than is really there.