I was thinking that maybe it is just a bend in the fabric of the corset. The corset is obviously made of thick or lots of material(the nature of corsets are that they have to be hard somehow, be it with boning or with a stiffer pattern...), so when she sits or thrusts her hip out or something, maybe the fabric just bends. Any thoughts from people who've made this dress already? Maybe the corset is kind of layered. Thinner, more decorative fabric on the top, and a layer of thicker or more sturdy lining underneath. I don't know....Just thinking outloud.