There was someone who posted about their Birdies, his and his wife's, and how short she is opposite to him. To improve the reach for his wife's Birdy, he installed a stem backwards, ie pointing backwards, bringing the handlebars closer. So that tells me there is a point where "one size fits most" won't work. Just not sure what that point is; however, simple solutions exist.
Did he ever say how tall his wife was?