Actually, the head looks good to me, but I'd expect a slash of highlight or shadow to indicate a muscle along the side of the neck reaching towards the collarbone, considering the angle of the lighting across her body for the rest of the piece. She's very pretty, though!
Not bad. The head is striking me as a little weird - maybe slightly out of proportion or something - but either way, for a 25 minute sketch, it's pretty damn good.