I'm 4'11". Since I don't know my inseam length or arm length, i don't know how much help I'll be.

I ride a 43cm Trek 2300 with 650 cc wheels. And it fits me like a glove.
I also ride a 47cm bike (touring) with 700 cc wheels. It fits me well, but I prefer the way the Trek fits / feels- but that could be due to a lot more factors than just bike size.

When buying my mountain bike (13 inch frame, Gary Fisher), the bike shop and I battled back and forth about them ordering it for me and if it didn't fit, whether I was committed to it. I can see it from their side as well (not a lot of us tiny folk out there and most kids my height aren't going to spend (or their parents aren't going to spend) $2500 on a bike... Luckily for me, it fits beautifully.

Good luck.