The Taylor Swift trajectory has unfurled with the cheery and ironclad inevitability of a Taylor Swift song. Like you or I, Taylor Swift was once 15, an age when (as documented in her song “Fifteen”), she was a lanky outsider “laughing at the other girls who think they’re so cool” promising “we’ll be outta here as soon as we can.”

And how.

Ms. Swift, whose public persona has veered from gawky to lovelorn, is now, at 25, the cool girl (albeit one very willing to poke fun at her own dance moves). Her rise has been steady over the course of a decade, but in 2014, she has soared to new heights.

She deaccessioned her twang, slipped the bonds of country music and traded her Nashville home (where America’s songbird sometimes received visitors in a human-sized birdcage, a décor touch ripe for analysis) for a loft in TriBeCa. She released a best-selling album, took on Spotify, performed at the Victoria’s Secret show and turned a tabloid reputation for man-trap desperation on its head, emerging as a single-and-loving-it cheerleader for girl power.