This might suggest that women are illogical in their selection of shoeware. But logic has nothing to do with it. It's status and sex appeal. The design and selection of women's shoes are based upon the notion that women become more appealing socially and sexually by squishing their feet into unnaturally small, tight shoes, preferably ones with well-elevated heels. Shop for shoes later in the day.
Feet tend to swell during the day, and it's best to be fitted when they are at their largest.
Don't rely on the size markings inside the shoe you are wearing or buying to determine shoe size. A size 8B from one manufacturer is not the same as a size 8B from another manufacturer. Also, keep in mind that feet become larger as they become older. Have your feet measured while you're standing. The end of the longest toe of the biggest foot should be a finger's width from the end of the toe box.