Somebody should have bought her a copy of “Fashion for Dummies.”

Then she would have known what a well-dressed mannequin wears for a joyride on the LIE.

Her turquoise jacket, open-necked blouse, and scarf were fine. And cops would have overlooked the fact that her wig needed a good brushing.

But she made one fatal fashion faux pas.

A cop — who clearly had never pulled over Anna Wintour on her way to the Hamptons — became suspicious because she was wearing sunglasses on an overcast day.

When her car stopped, the eagle-eyed officer also noticed her summery jacket was belted with string, the sleeves artfully bunched with elastic bands, and the scarf was cheap winter fleece.

Not to mention the fact that she was missing her legs.