Further rationale to measure the clothes:
--Even today, a given size isn't necessarily the same from company to company.
--Even if one buys off the rack, clothes can still be altered to fit the individual. For example, I usually have to shorten my pants. And I think alterations were even more common years ago, when clothes were more expensive/less disposable, and home sewing and use of tailors were more common.
So I agree, direct measurements of clothes that were last worn by AE, with no subsequent wearers, are the best bet.