Sorry this is so uncomfortable for you. But providing that she's not engaging in actively bullying you, she can ignore you if she wants.
Yes, the weight gain comment probably has a bit to do with it and it's possible you've said other things which have sat poorly in the past which she hasn't told you about. Thing is though, there's no rule to say that one must be friends with everyone or that they must forgive. She's made her choice and there's nothing you can do about it other than accept it, learn from it and move forward.
good luck
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.