Hey, So I went to the website and looked further at this top. http://www.shareenvintage.com/shop/shareen-again/day/shareen-again-batwing-top-295.html
And this is my estimation of what's going on (excuse the terribleness of these pictures, I'm a sewist not a graphic designer!!!)
So the one I just linked to has horizontal strips on the back and vertical strips on the front and a back center seam.
So, she started with a Sari
Then, I'm not sure about the angle of this cut or the proportions of anything, but maybe she cut it something like this
And then made the back center seam by sewing it like this
Then, you fold the sides to the top (meeting the numbers) creating a small arm hole.
Again, i'm not sure about the proportions, but this is the basic idea of what seems to me to be going on.