Hmm. I suppose the concept is sound, but the anatomy is screwed up. Her waist looks like it'd bend backwards with the force of gravity, her breasts are huge, and her pelvis looks crunched. It looks like you were focusing more on making her look 'sexy' than drawing a character that could actually stand on it's own. I recommend you NOT look to anime and manga to learn anatomy. It shows in your work.
I know some people are ragging you that she does not look like a troll but I remember that there is a book where the male trolls are all the fugly things that every one seems to think about and the females were these drop dead beautiful giantesses.
So don't let the comments get you down.