Alright, I fail spectacularly at the redline bit, so I'll leave that off for now. My English is also not very good today, so I hope to be clear, but can't promise to be. XD;
What I notice is that your female is sitting up straighter than the girl in the picture. This seems partially because of the way her butt is positioned. The girl in the picture has a curve to her lumbar area, which basically allows her tailbone area to be flat on the ground.
Your girl is sitting on the bottom of her butt, the other girl is sitting/half-lying on the back of her butt.
That will allow you to put the underground a little higher as well, and give you the better angle with the legs.
Your girl's head seems a bit small compared to her legs, but maybe once you shift the picture a bit, that'll not be as much of an issue. Otherwise, should probably make it a bit larger still.
Hope that helps.