I'm 5'1" and my road bike is a 44. It's a Specialized Dolce from a few years ago. When I bought my tri bike I got a QR extra small and the fitter said even that was pushing it. I guess I'm a pretty squat little thing... Funny though, my girth makes it all an illusion. I actually think I'm square!
Keep looking until you find one that fits. It may need to be a special order situation. And DONT buy it when they say they can "make it fit" by adding shorter stems etc.. It's just not the same!! Believe me, I bought that... once.. NEVER again!