This lovely lady is the one and only C.Z. Guest.  She was an American actress, socialite, horsewoman, fashion designer, columnist, who’s clean cut and classic fashions define American Fashion.

from Voguepedia:

C.Z. Guest stands out among Truman Capote’s fabled swans as the most serene and unruffled of the flock. With her sleek cap of champagne-colored hair and eyes as blue as her blood, C.Z.—the “cool vanilla lady,” as Capote described her—glided among the gilded lilies of the day with an “ice cream reserve”that matched her exacting sartorial choices.

“She dreads overdressing as she would adders fanged,”Vogue observed in 1959.  Unlike many of her set, who gravitated to the latest fripperies from Paris, Guest eschewed both frills and trends, cultivating instead an aura of polished refinement. “She has firm, even inflexible ideas about how she looks and what suits her… . She buys nothing solely, or even primarily, because it is ‘fashionable,’ ” the magazine noted. Accompanying the story was a photograph of the subject wearing a double strand of pearls and a pale-gold column by Mainbocher—the American master of simplicity who “might have been divinely appointed to be Mrs. Guest’s dressmaker.” C.Z. would remain loyal to her favorite couturier until Main, as she called him, closed his doors in 1971. “I like fitted clothes that show off the body,” the whippet-trim socialite once said. “My style was his style.”

C.Z. dressed impeccably for every occasion. Whether scooping up another silver cup at the races or mingling with masked society at the 1966 Black and White Ball, her strikingly simple choices turned heads. “I like the classic look,” C.Z. once said. “Keep it simple. There’s only so much you can wear.”

She a) is a fashion inspiration, b) can pull off all white lie nobody’s business, and is c) just really hot, even when she was older