Oh, honey.
Just remember, parents are just people, and sometimes they're sh*tty people. Your mom was simply going for the soft spot, the thing she knew would hurt you. If it was me I'd wear a perfectly fitted dress that I adored and looked AMAZEBALLS in, and just as I reached her seat on my march down the aisle, I'd lean in and whisper: "How do you like my fat *ss now?", and then just keep walking.