Watch out, Magnolia! The West Village cupcake institution may have Sex and the City fans galore, but Chelsea cupcake cafe Billy’s Bakery has been infiltrated by the real fash crowd. Just in time for Mother’s Day, designer Rebecca Taylor has created two cupcake designs inspired by her spring 2009 collection. Vanilla Twinkle consists of Billy’s yellow daisy cupcake topped with blue vanilla buttercream and a sprinkle of white crystal sugar and silver dots. Mocha Meow is created from Billy’s chocolate cupcake and special Mocha-flavored buttercream with dark and light chocolate sprinkles. The Rebecca Taylor Mother’s Day cupcakes will be available beginning May 1st. Now if only they were calorie-free…