Here is a fast lane critique of the photos.
#1 Expression problem. Eyes dark, no catchlights. Too dark below model. Pose is somewhat awkward. Looks like you burned in the area below the torso.
#2 Pose problem. Big crease in back from twist she's in. Black background is distracting. No catchlights.
#3 Legs flatten out when flat footed. Wear heals, or have model raise up on toes at the moment of shot.
#4 is best of 4. See three about legs. Both #3 and #4 have uneven background light (minor detail).
Re: This is Sarah - Please critique
cheers,
rfs