The most difficult thing for people when beginning to make portraits is thinking that a portrait really has to be a portrait. Are you making a photograph of a person, or a photograph of what they're wearing?

#3 and 4 seem to want to think they are fashion photographs, but they don't stand up to the weight of the challenge. I'm partial to #1, tonally and compositionally, although the fact that the strongest highlight is on her shoulder instead of her cheekbones or something is a bit offputting because it draws your eye to an out of focus area of the picture that isn't really more interesting than the focal point. #2 looks more to be a picture of a girlfriend or something, rather than a "portrait" of someone else. Whether you want to communicate this sort of feeling sort of makes or breaks the photograph...I find these sorts of pictures more interesting as part of a narrative grouping, rather than one offs.