Tiny. 43cm road is going to be too big. A 12" mountain may be just about right. My slightly taller wife (5') rides a 14" mountain bike and a 16" road bike (40cm). Unfortunately, finding that size bike is not easy. It's even harder to find one used. This one for instance, is probably too big, especially with the 100mm travel fork.

This one might be better but I'd bet it's not quite extra small enough.

Look for Terry Cycles. My wife got a Symmetry about a year ago and finally knows what a bike should fit like. They are a little wierd (24" front wheel) but it is a sweet bike for her.

I do have, in my garage, a 12" Jamis Durango frame which is a really nice frame for a very small person. However, it's just a frame which isn't a cheap route to go for a complete bike. PM me if you are interested.