We can see females can do the splits, make a complete ball of themselves, kick over there heads and put their feet behind their necks. Pretty sure they can do something as simple as bending their backs in all sorts of flexible ways males can't. Even easier for females to bend their hips in all sorts of crazy ways. If the female can do the T splits they can move their hips however they want.
Unless your talking about how muscular that twl'iek is or how she seems to not have any lower rips. In the past some woman would have their lower ribs removed so they could do thinks most people can't do in flexibility. I don't know much about twl'iek biology but they sure can dance in flexible ways.
I understand how human physiology works. I'm just saying that stance is very unnatural and looks like she'd be in a great amount of pain to stand that way. I'm not saying you cant bend that way, I'm saying you cant COMFORTABLY bend that way, especially not while standing. She'd either be in a large amount of pain or be severely unbalanced. Also, DID she have her ribs removed? If that's part of her character maybe you have a valid point (if we forget that her spine exists) but if she didnt, you may as well say she had her tonsils removed.