Here's Enid's size3-4 princess line dress.
And here's my own size 4 A-line dress draft. (From Aldrich)
Now obviously this isn't an apples for apples comparison - I would expect a size 3-4 to be smaller than a straight 4 (although not by much) and my A-line draft is slashed and spread right from the shoulder and so adds width through the torso as well as the skirt, whereas the princess draft actually nips in at the waist (this is optional). What I noticed particularly is that the armholes and neckline are pretty small - noticeable even on Nicholas (yes, he insisted on trying it on but lost interest before I got out the camera) . Her shoulder angle is very good on Isabella (it's being distorted a bit by the tight armholes), better than mine.
Next task is to compare her bodice draft to my three and four and see how similar they are, particularly in the neck and armhole. I wonder how much of the snug fit is due to the prevailing styles of 1951, and how much is due to the smaller size, which I would expect to be no more than half a size. I haven't yet found any size charts for Enid Gilchrist's patterns so it's hard to tell exactly what the intended fit was. Is it odd that this sort of thing fascinates me?