I think out of the whole image, I love her lips best. They're vibrant and I'm not sure if it's the angle or the way they're painted, but the upper lip looks so dramatic and curvaceous from a normal female upper lip.
I love the pasties as well. I thought they were jewelry at first. But yeah, her lips and face/hair is just so awesome ( can't think of a better word ) it naturally inspires one to try and recreate it in a drawing. Or maybe just me.
Either way, fantastic job and tell your model she is lovely.