Very pretty face. Great colouring and shading, too. One thing I notice, though, is that she's not making use of the chinrest of the violin quite correctly. The curve of the left side of her jaw should be nestled in the chinrest.
One way to explain it would be that the image is capturing a moment when she is still in the act of bringing the violin and bow into their proper positions, but something catches her eye. If this were the case though, perhaps more separation would bring this across better. i.e. the violin further away from her head, and the bow not touching and not close.
Now that I look at this the next day, I think she's even prettier than I originally supposed. Well done.