Tinsley Mortimer and beau Brian Mazza are playing house. The reality star and the hospitality executive were overheard telling friends at the reopening of Murray Hill lounge The Loft at the Hill that they’ll share a house in the Hamptons this summer. They’ve been dating since they met two months ago when Mazza appeared on Mortimer’s CW show, “High Society.” The couple will likely spend nights at Dune in Southampton because Mazza works for Paige Management Group, which owns the club.