Originally Posted by icemilkcoffee

I have some experience here from when I was looking for road bikes for my wife who is about 5'1" and my kids who were about the same height a few years back when they were younger.:
1. Conventional 48-50cm 700c frames: kind of awkward geometries with too long top tubes, but these are good for people with long torso and long arms and relatively short legs.
2. Terry bikes - these are good for (mostly) women with typical long leg/short torso/short arms body type. But let's be honest- these do look a bit goofy.
3. nobody brought these up, but another option is 650C wheel bikes- these are sort of between 1 and 2. Both Trek and Cannondale made a series of 650c aluminum framed bikes back in the mid 90's to early 00's. Felt and Fuji made some from in the 2010's. If you insist on Classic steel bikes, Centurion made a 650c version of their Lemans around '88 or '89, and Bianchi also made a 650c Eros in the 90's. I feel these are the best bikes for small riders. The main drawback is that tire choices are limited. Although you do have the pretty decent Panaracer Pasela 28mm folding tire. Earlier there were no TPU tubes for this size, but I just checked again and Ridenow does have 650c TPU tubes now! Here is the 2002 650c Cannondale R500 I bought for my son. The crankset is a 160mm Origin8 and the brifters are short reach Microshift R9: