I didn't mean for this to stay an incentive for so long, but it's finally been replaced, so here it is! Accommodating for the tail is probably not something you would forget if you had one but I thought it was funny, so it was drawn anyway. Sorry.
This is better than anything I could ever draw, it's great. But wouldn't it be physically impossible to stare at your own backside? She'd probably be more likely to look over her shoulder rather than being able to rotate her torso 180*. If you used a feline character, then you could probably say she's just flexible. But amazing skill, nice work.
The torso isn't 180 degrees otherwise the shoulders would be lined up with the rest of the body. The torso is twisted to the side, and her head is also turned. the torso is only turned 90 degrees, and the lower you go, the less turned it is. The anatomy is correct xP
I understand exactly how the pose works, it's not the easiest to explain, and when it comes to anatomy, art makes things tricky because you're putting something 3d onto something flat, but it is correct.. Maybe a little off but not very much at all