Terry is indeed specialized in women cycling and was using 24" ETRTO520 wheels for the smallest women frames.

Bikefriday has a sizing from in which they ask for inseam and for the geometry of an existing bike that fits the customer.

Trek has women bikes of all kind.

Giant has Liv a special brand for women...

Now its a fact that there are less female cyclists than male cyclists and that the market for women bikes is smaller than for men bikes, especially in high end bikes (its less the case for utility bikes, city bikes, cargo bikes...).