Glare!
I absolutely love the girl on the right. She's very well done, from the hair to the expression, and especially the hand. Excellent detail! Excellent shading, as well. The left girl's face is strangely put together. Her mouth is way too far up, too close to the nose, which, for some really strange reason, is covered by a star. Considering that the right girl's hair is so well done, where you can see individual locks of it, the left girl's hair, which has stylized hair that ends in straight lines and looks as though she has massive blocky locks of hair, seems too unrealistic in comparison. Not that I hate that way of doing hair, it just doesn't fit when the other girl has such detailed, realistic hair.
The glare in the center is distracting!
Besides these little flaws, this is really good. Your capacity for detail is astounding and you have great shading.
