It sounds to me like your friend is jealous. And if she's jealous just a few weeks after your surgery, just think how bad it will get when you start dropping pounds and getting compliments from everyone.
Just nip this in the bud already. If she's not with you, then she's against you. In my own life, I have cut ties with friends who were negative, or made snide remarks. I just don't need that kind of energy in my life. If she comes around and acts like a true friend, then great. But if she keeps up the negativity, then maybe it's best to part ways.