A 650b frame would have better geometry. My 5' 2" wife has one and loves it.
The traditional 650b tire rides like a dream.

The choice of 650b frames is a bit limited. Rivendell makes the Saluki, but it's expensive. Kogswell is supposed to be good, I haven't seen one yet.
http://www.kogswell.com/products.html

You could also take an old hardtail mtn bike (try to find a decent steel frame)
and put smooth tires on it. The Bridgestone XO series was a nice 26 inch bike designed for general riding. I had an XO2. The star was the XO1, but they typically get traded for close to what they cost new. Anyway, if you could find one in her size, that would work.