Don already got most of the basic answers to why Georgina Terry made frames for women with 24" front wheels. Another basic reason is it loweres a level top tube so that shorter legs can straddle it. Smaller women can typically have around a 28" inseam and putting a brake, headset and lugs above a 27" tire doesn't give enough room to stand over the top tube.
I'll just add a bit of history to this concept. I Believe Bill Boston was the first to make a frame with this combination. At least he was the first one I heard about that did it back in the 70's. Georgina is not a big women and probably was glad to copy that idea to fit herself. Sometime in the 80's she went from being an individual framemaker to hooking up with a marketing guy and expanding her business with other framebuilders in their employ (I seem to remember some of them came from Serotta when he had a slow down). The 24" front wheel then became an identifying marketing approach. Something akin to Hetchins curly stays. It made a visual statement that this bike is made specifically for women.
One reason a 24" wheel was used (as opposed to another smaller size) was because it is a size that at that time was readily available. I've made a lot of bikes for small women over the years and one thing I've heard them emphasize a lot is they don't want 2 small wheels that would make their bicycle look like a toy. That emotional feeling was always mighty strong. A 27" back wheel takes away the kid aspect of it. I got the feelings each one had been teased a lot about their size and they sure didn't want something that brought the subject up again.
What makes more sense for today is using two 650c wheels - a size made popular with the tri crowd but rare back 25 years ago. This has several advantages besides not having to carry two different size spares. First it makes a small bicycle look proportional. The lugs are not crammed together like they are on a small 700c frame giving the impression something isn't fitting right. Smaller wheels are also lighter wheels which provides advantage for the less powerful rider. I've heard a lot of people say they think 26 inch wheels are harder to pedal because of the gearing (you've got to pedal faster to cover the same distance) or there is noticeably more rolling resistance or some other nonsense. I trust CR members are smarter than to believe those things. Another advantage of 650c wheels for women is that, unless they are racer types, it steps down commonly available gearing (that often starts with a 53/12 or 13) into a more useable range for someone not on a training ride. A 52/13 gear on a 650c bike is about the equivalent of a 52/14 on a 700c bicycle.
And finally when fitting a women, it is almost always necessary to have the handlebars as high as the seat. This means she rides a typically bigger frame than a man her same size. Their crotches don't like extra pressure when they lean over too far. What is a comfortable position for a man is not for a women.
Doug Fattic in Niles, Michigan where as many frames have been made for women as men.