On both front and back, draw the new neckline and redraw the side seam reducing at the hem, then draw the bottom part with the slash lines for the flounce.
Draw also the underbust line. on back only, reshape the center reducing the dart.
On front only, widen the shoulder dart by 1cm at the neckline and redraw the waist dart making it more fitted at the underbust.
Reshape the sleeve to make it more fitted and draw a slash line at bottom.