Okay well I ride a 50cm and I am 5'3". Height is not the judge. It's leg length, torso length, arm length and other factors.

All of this "Well I have a friend who..." reminds me of "He's just not that into you."

I suggest going to a shop with a fit kit.

Or... okay I'll be the one... check out Craigslist, find some bikes with decent components between 50 and 53 cm, take a few test rides, if one feels good spend a few hundred bucks on it for a starter bike and see if you actually like road riding. Then save your pennies for a higher end bike down the road.