"The Spring Hat."

A portrait of a lonely spinster, the hideous hat she creates for the wife of a man who attracts her, and her bewilderment at the "mystery [of] how one person got into the way of being entranced or familiar with another."

In Now Sleeps the Crimson Petal and Other Stories/The Enchantress and Other Stories (1961). Published first with title "Miss Manktelow" in Housewife (January 1953). Reprinted in The Treasury of English Short Stories (1985).