Maybe I shouldn't answer questions when I'm cranky, but why the **** didn't you pick a dress they'd ALL look good in? Blah blah, you refuse to change the dress, well you know what? It's your fault. Sure you can ask her to lose weight. You ask her like this "Hey, look...Would you mind getting in shape? I'd like you to feel as great as you can on my special day" - sure she may see through that niceness BS to the superficial crap that it is, but, honestly, no matter WHAT you say, as nice as you make it, it's going to look as bad as it is. Sorry, that's the truth. Unbelievable. You pick the dress, then you ***** about how someone looks in it. You choose a dress they ALL look good in, that suits ALL their frames and that compliments your colour scheme. Otherwise, what the hell is the point? You may as well just go to rent a bridesmaid. It isn't about supporting you on your big day obviously, it's about looking good. You KNEW she was big when you chose her, unless she packed on the pounds the moment you chose her, you have no right to ***** about a dress SHE doesn't look good in. Why would you pick a dress only 3 out of 4 look good in?? If you're fretting that much, you should ask ALL of them to "support you" while you start a "fitness circuit" or whatever. Sugamama has the best idea, but I'd go further and not ask just her, because she WILL see through that, but ALL of your bridesmaids to "help you get fit".