Bravo debuted “The Fashion Show,” its “Project Runway” replacement, on Thursday night, and despite tough reviews, the first episode — featuring Isaac Mizrahi, Kelly Rowland (formerly of Destiny’s Child), IMG senior vice president Fern Mallis and Harper’s Bazaar’s Laura Brown — drew 890,000 average viewers, according to Nielsen. That figure easily beat out the first episode of “Project Runway,” at 354,000 viewers, but was far from the 2.4 million viewers the show averaged during its fifth and final season on Bravo (if anyone hasn’t been paying attention, it’s now moving to Lifetime). Mallis invited friends to screen the first episode Thursday night at the penthouse suite in the W Times Square; Rowland wasn’t on hand, because she was in London, and Mizrahi was en route to Bridgehampton. Mallis said future episodes will feature Charlotte Ronson, Erin Fetherston, Peter Som, Norma Kamali and Vivienne Tam. “We still have two episodes left to tape, including the finale in July,” she said.