Why on earth would a person refuse to befriend another simply due to their physical appearance? That doesn't make any sense.
On your friend, there are two possibilities:
The first, and less troubling, is that she is simply very blunt. Perhaps in her mind, pointing out that your tummy pokes out in dress is alright because she would want someone to tell her if ever she were in the same predicament. Maybe she doesn't realize how bothered you are by it. Or maybe she just doesn't think before she speaks. As a blunt person, there have been many a time when I've said things that, in retrospect, the other person had reason to be miffed at. After an elderly man-a very, very elderly man-told me to "have a nice life", I responded "You too, or at least what's left of it." Now I realize that isn't something you say to people, but at the time, I assumed his age was more obvious to him than it was to me and I had no problem saying it. And that is but one of many examples.

The second is that she is a bad friend, plain and simple. Constantly pointing out your flaws even knowing how much it bothers you when she does so indicates she is attempting to keep you at a lowered state. Does she nitpick at how you do things and how you dress as well? Is she quick to point out every teensy little flaw? Do you leave her feeling as though your self-confidence has been crushed into powder?

My advice would be to-if you've not already-talk to her about how these comments make you feel. If she is simply very blunt, she will, upon learning how her habitual critiquing has troubled you, stop. If, after telling her, she continues her judgmental behavior, it may be best to go your separate ways.
I understand that is hard for people to do, due to the fact that people form emotional attachments to each other, so I do hope this does not have to happen. Unless you think it best.
It is rather vexing when a person points out a flaw which you are already clearly aware of. The next time a rude person calls you "fat" look down upon yourself as though you are seeing your body for the very first time, slowly lift your head and, with an expression of pure horror, look into his eyes and scream.