Looking through this I am left with the conclusion that 50cm frame height is about the limit for 700c tyres (judging by the range of frame sizes on offer from various builders. The Mercian upstream falls into this category).
Here are a couple of bikes used by my smaller (male) clubmates on our recent Auvergne outing. The owner of the CBT, which is on 650c wheels, also has a tourer which is on 26" (and flat bars). I am fairly certain that the owner of the Berthoud (26x1.25 wheels; he had wanted it to take 1.5 tyres but not enough clearance with the guards) also has a racer on 650c wheels. He also has a tandem on 700c but I can't remember how the frame works out! These bikes don't fit the requirements of the OP but they do show how smaller wheels can be used to reduce frame size.
Another small clubmate also has a 650c road bike, a Decathlon which I think went out of the catalogue a while ago. He isn't quite as small as the owners of these bikes but he finds it a better balanced option for him than 700c.