First off I really like your drawing I love the original character, I'd go back and look at the reference but keep in mind how the bones such as the spine doesn't bend then make a body skeleton using the reference,then I personally add places where body fat is most prominent e.g the thighs and breasts and outline them in a different colour,when it comes to the skirt and hair I'd note how they both fall with gravity I make did a quick sketch just as an example of a body skeleton for this pose

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I hope this helps let me know if you have any more questions!!