Already the market is hurting a girl's self image

Last weight checks at dr's offices, Madelyn was only one pound over the boys. Her legs have slimmed down a lot in the past couple of months since she's running around more but she's still the same size as the boys. Look at this photo - the left is a pair of Andrew and Nate's shorts (size 24 month) and the right is Madelyn's (size 3T). Not only is hers a 3T, it fits tight and when she bends over the back falls over the butt and I'm sure it would show if it weren't for the diaper. However, Andrew and Nate can walk around the house and their shorts start sliding down over their hips on its own. Not only this, look at the length. She's two - not 16, and I don't want my 16 year old wearing shorts this showy either. Call me old fashion, but I'd like for my daughter not to be known as the girl with nice butt cheeks and shapely thighs (although she has some big ones like me). How long will it take for Madelyn to wear sizes smaller than her brother's? If she doesn't, I don't care but she will one day.