Cookies might be the enemy for waify models, but rumor has it that Erin Fetherston and LU Biscuits will collaborate on … something. Fetherston burst onto the fashion scene a few years ago and is known for her whimsical, otherworldly couture dresses. Recently she branched out to ready-to-wear and will present in Bryant Park four days before the collaboration will be announced. She recently gave a one-word description of her upcoming collection: “Sunset.” So what the designer and the chocolate-biscuit company could be making together is anyone’s guess.