Niice =)
I love the hair and how it runs of her face almost like water. I also like how you've done the eyes and the mouth (Well, the face in general is actually really good). I would say, the reason a few people think that she isn't supposed to be slouching is because you've just made the shoulders raise, rather than make the neck and collarbone look more tense. It's just my opinion and you can do with it what you want biggrin
I also really like the elaborate detail in the kimono and sash. I wish I had such an eye for detail razz
Good job!Edit: I just also thought, well, unless you really wanted the angsty expression, I think that she would look more graceful and beautiful if you made her look relaxed
xD