What you've drawn there is Egyptian hieroglyphic art (albeit with the face turned toward us). The twisting of the upper torso is lost. You can notice that she isn't turned all the way to face us because you can see the depth of the rib cage under the armpit area. In fact, it's rather terrifying, what you have there, as though her lower and upper body were chopped in halves and then stuck together in a 90 degree angle, lol. Perhaps that line extending from the collar down to her lower right hip, where the clothes overlap, tricked your eyes into thinking you preserved the twist?
If one can't see the underlying anatomy beneath the skin, then one certainly can't see the underlying anatomy beneath clothes. I would suggest that referencing naked or close to naked pictures of people would be most beneficial? A good exercise you can try (that I've yet to make a habit out of) is to draw a skeleton over whatever naked reference picture you choose. If you're interested, I'll suggest
this video series, where he does just that, in addition to teaching you the individual big skeletal structures. Visuals are neat and helpful, he explains things well, I would recommend it.
The problem is, if you don't at least have a basic understanding of anatomy, you don't know what to expect to look for, so you end up only picking up what you want to see. Which in this case seems to be a regard only for general contours. Which you seem to have done well enough. You want to beat your brain, since your brain will trick you into drawing things you think you see or overlook stuff it doesn't know to look for!
e: also notice how in your sketch, everything is aligned perfectly down the middle and is very stiff. While in the reference pic, motion starts from the top of her head. Her head is tilted to the right, there's a slight curved slant from the upper torso/shoulder area down to her hip, and then a big swoosh out to the left with her leg. Making a giant 'S' shape. More organic than a straight line. Perhaps try look for these overall curves when challenging the next reference picture you choose?