Synopsys from goodreads:
Julia, a hip, downtown salesgirl at Pelham’s jewelry store, finds her social life turned on its head when she is asked to deliver a necklace to the store’s young heiress, Lell Pelham, on Lell’s wedding day. Beguiled by Julia’s earnest cluelessness and her vintage-chic vibe, Lell and her gang adopt Julia, and “Eliza Doolittle” her into passing as the heiress to a family fortune, just for a laugh. Dazed by the whirlwind of trust funds, pedigrees, Cosmopolitans, and penthouses in her new world, Julia is unprepared for the ardent advances of Lell’s husband—or the vicious claws her new “friends” develop when they decide Julia is an ingrate, and demote her from society goddess to penniless cling-on with one well-timed editorial. Suddenly, she must return the borrowed couture clothes and try to remember who she was before the body snatching took place. Hilarious and completely addictive, Wolves in Chic Clothing is a modern-day rags-to-riches-and-back-again fairy tale that will leave fans stamping their Manolo Blahniks for more.