I'm 5'1" myself so I understand your size issues. I assume that you currently have a Terry bike. Honestly a new Terry bike might be your best option and the Terry Fast Womans bike looks nice but not cheap. I have a custom 650c wheeled bike and honestly its only JUST small enough for me for good fit. Even factory 650c bikes are too big to get good fit but then again I did ride a 700c wheeled bike for a while. You can do it but the issue is GOOD fit. It will look cooler but it won't fit for quids.

If I was going to have to ride a standard factory bike I would be going for this one, http://www.bianchiusa.com/06_junior_24.html

COOL as! You would need to change the cluster and chainrings for higher gears though but you WANT to keep those cranks. Just the size someone our height needs and there hard to come by. I use custom 140 mm cranks myself. OK its 24" wheels still but they're both the same size and it looks great!

Other than that you could go custom 650c like me but that costs $$$



Regards, Anthony