This is quite an interesting article:
Womens Specific Design Bikes – Pointless or Innovative?
Basically, it claims there are three approaches:
~ Completely different bikes, inc frames (shorter TT, etc) eg Liv
~ Same frames, different contact points eg Juliana, Trek, Specialized
~ Exactly the same, but in smaller sizes eg Pivot
I’ve never really understood why manufacturers don’t routinely fit smaller components on their smaller bikes (such as shorter cranks, narrower bars). So I was pleased to see the new Rockhopper has 29″ wheels on the larger bikes, but 27.5″ on the smaller frames.