Yes, we difinitely need more physical measuremants than just an overall height.

There are several options besides a 700C. One of the most popular was the 700C mated with a smaller wheel (650C or 24"). This permits lower top tubes by virtue of the shorter fork. The smaller diameter front wheel allows a shorter top tube without increasing toeclip overlap with the front wheel. It also permits standard gearing, but has the disadvantage of having to cary two sizes of spares and the selection of performance 24" tires is not very good. However, it permits down to about 45cm, with a horizontal top tube and top tubes as short as 48-49cm. Models in this configuration included the Fuji 450SE (search on this, there are threads on this bicycle in this forum), Nishiki International and Prestige, Panasonic DX2400. Bianchi Sport DX, Miyata 512, Shogun Samurai, Bridgestone 550, Centurion Ironman Expert, Lotus Elite 600, KHS Triathlete Pro and numerous Terry Precision models.

The other option is 650C wheels. This gives a moderate decrease in frame size and top tube but has the advantage of only having to carry one size of spare and a good assortment of performance oriented tires. It's also slightly smaller than the suggested 650B. These bicycles are readily available in a variety of brands due to their popularity with female triathtletes.

In 700C, the frame size limit becomes about 48cm with top tubes around 50cm. This can be cheated by going to welded construction and sloping top tubes but top tubes remain in the 50Cm region, unless you're willing to accommodate an increase in toeclip overlap.