Alex
Shooting portraits like this is notoriously difficult but well worth the effort. If you look closely at your image you will notice that most of the image space is taken up with her back...and there is nothing of interest to see there. Human backs are rarely interesting. Her face is given only a small part of the image space but we have no eye contact or expression to hold our interest. Her hair takes up a great deal of image space and once again...not much to hold our attention. Her hand and her lips are the most interesting part of the image but of themselves are not exciting enough to make the image sparkle. Can you see where I am going with this? With female portraits we want to see eyes, body curves, expressions, attitude, light and shade, fashions, sexy poses, classical poses and beautiful backgrounds. Long legs, breasts and cleavages, mystery, seduction, purity, innocence, agression, power, fragility, lace, health, vitality, beauty, pride etc etc. You have a great
model and you need to go back and liase with her to come up with creative ideas in order to produce better images. Champagne and music are 2 well tried aids. But not if she is your sister.