(Description from DA)  
Rarity, humanized and colored.
 
She stares at your outfit disapprovingly.
 
Character copyright Hasbro/Lauren Faust
 
Edit : Before commenting, please read other comments which have been posted. Yes, I am fully aware of her monster legs. This was a design choice rather than an anatomical mistake. Rarity is a fashionista, not a model. She would not have the physique required for the modeling field, otherwise she would have been chosen rather than Fluttershy as a model. Taking this into account, I figured the easiest way to make her unsuitable for that venue would be to accentuate some part of her anatomy, or overall make her thicker than usual. I wanted to give her the appearance of someone who at some point tried for it, and likely tried too hard. Legs are very important in a modeling career - monster legs will shoot that down.  
Additionally, these legs are not particularly monstrous. There are larger in life, including on people with this type of build.
 
So before you go “ahurr hurr she got hueg legs,” please consider that it’s already been said, and will likely just make you look like a prick.