I took a stab at a quick edit of the bra-and-panties version of the character.
The gore of the bra (the bit that connects the cups) felt very wide-set in your original image. Real bras tend to have closer set and often higher gores, though a high gore would reduce readability too much and make it look like a flat straight-across bandeau. I made the cups a bit larger and fuller, to indicate the shape of the breasts and to make a narrower gore. I also removed the really dark shading there, which I assumed was meant to indicate cleavage (?), but ultimately just looked... kind of like chest hair. I kept some lighter shading. I recommend looking at some pictures of women in well-fitting (as in, don't google Victoria's Secret or something) bras for shadow reference. Warning, the following link is a picture of a woman in a bra:
image. Note how there's really not all that much shadow or true cleavage there. The art style you're going for will benefit more from looking at examples of well-fitting bras rather than trying to indicate anime-style cleavage.
At the risk of turning them into full-on granny panties, I raised the sides of the panties a bit to help indicate her waist, since I felt that wasn't particularly defined.
I also lowered her head a little bit - previously, her neck looked really broad, almost like a weight-lifter or something. Lower it allowed me to narrow it without turning it into a giraffe neck. I will say I'm not quite sure if I like this, though, as I feel as though it comes at the expense of a bit more stiffness to the sprite. The original way the neck sat felt a bit more relaxed.
Finally, I made her back arm a shade darker overall to indicate a bit more depth.
For the animation: I feel like the torso and hips are very stiff. They should move with the character as she walks, not remain static. The feet might also benefit from a bit more attention in particular - the way she sets them down and they never change shape is a bit reminiscent of a horse? The human foot is much more fluid and will bend upon impacting the ground.