Well, her cape is not a half circle, it's fitted (much like Batman). So the neck & shoulder area are completely different in their construction.
This isn't bad, it's got a collar, which you need, as well as the fitted shoulder. Major modification to the front is obvious.
The bottom points are easy if you are going to line the cape (which I recommend). Once you have the cape cut (without scallops) but not assembled, make a paper copy of the lower 12" or so. Determine how many scallops you want, I recommend an odd number (the art shows 5). Fold your paper template in half and work from the center fold out. measure the distance, divide by 2.5 and that should be the diameter of the circle you need. Use a compass and a ruler to draw out the half circles along the bottom edge of the template paper, starting with a quarter circle at the center fold. Because you are doing this on paper, you can tinker with it to get them just right, make them deeper or shallower curves, whatever suits you.
Once you like it, use this template to cut the bottom of your cape and lining fabrics. When you sew these two pieces together, remember to clip your curves and iron before attaching the cape to the shoulder pieces.