I'm very sorry about that.
I guess that maybe they would have had some bad experiences in that way, as here have been on fashion the cloths too "small" between teenagers. Some girls who weren't too tiny couldn't find some kind of clothes. Even the government negotiated with cloths makers to change the sizes trying to minimize the anorexia problems...
I think this rude way to say things could be more common in big stores for teenagers like Zara, Mango...although thre is also kind people in those places...