It’s fun to guess that Lisa Immordino Vreeland’s first movie may have been obliged by betrothal. “Marry me,” he purred, “and I promise you’ll one day make an entirely unchallenging film about my late grandmother!” With couture-chronicle chic still apparently active in documentary circles, what chance did the new Mrs. Vreeland stand against kismet? The old Mrs. Vreeland, outlived by her reputation as “the empress of fashion,” already had bestowed the legacy of everything we think we know about modern glamour. Anyway, as a family-approved portrait of a bon vivant, this will suffice. It falters with actors overdoing performed transcripts of interviews between Vreeland and George Plimpton, who helped on her memoir, but scores with animated page-flips through old issues of Vogue and Harper’s Bazaar whose Vreeland-edited style spreads still seem remarkably new. (Behold here young Mick Jagger, as if for the first time.) It also knows enough to have the exactly right title.