Jennifer Lopez is back on the floor. The “Jenny From the Block” singer, 57, danced her way into the Vogue World Milan show on Tuesday night, taking the hand of a male model from her front-row seat and stepping out to the center of the Galleria Vittorio Emanuele II. After a spin, she raised her arm with a flourish. The moment put her jaw-dropping Dolce & Gabbana necklace in motion, too. The piece, from the Italian house’s high jewelry, or Alta Gioielleria, collection, is a white gold and diamond design anchored by a 74.459-carat Paraiba tourmaline. It was previously worn by Princess Diana’s niece Lady Kitty Spencer at last October’s Grand…
