You know, I really do feel this is a definite improvement. Just drawing the background alone made this picture look so cool. There's a background to ground her in her surroundings, the color palette works to set the mood (it's cloud and all the colors are muted with only reds and blues, love the choices of color), and it just all works. I even like Nina's expression and how it works with the rest of the picture, along with those adorable freckles.
I say one hint I could give to improve the picture is that, since her legs are underneath the table, they shouldn't have the shines the rest of her body has because the table will be casting a shadow. Either remove them completely or just reduce their opacity by a lot to create the illusion. It's just a minor thing, though and doesn't detract from the picture.
Great job! I can honestly say I would love to see more pictures done with this level of care.
I absolutely LOVE the way you draw Nina, she looks so cool in your style, and I like how you give her blue freckles underneath her eyes. She looks extremely cute!!! Also, I love that shine effect you give your drawings, it's interesting.