Imho, its all about skin color. If she was blond and blue eyed, she would be red hot in the modeling world. There's a lot of extremely successful "shorter" supermodels out there. Kate Moss, Laetitia Casta, Devon Aoki, just to name a few. She's gorgeous and has a stunning presence in print, its just too bad that that industry is still so color blind.
I get this feeling too. It's not very much about height, although it IS a problem...but look how many short girls do well if they have a great look. I can only think of one non white short model who is around 5'6". Look at Amanda Norgaard for example as a short/white model who is 5'5"-5'6" max (seen her before in person REALLY short)and it wasn't that tough for her to book not only good money jobs and editorial work, but also runway!