HEIGL’S MOMENT: Katherine Heigl, who attended the J.Mendel show in the designer’s silk floral jacquard off-the-shoulder dress, is expected to start filming “North of Hell” with Patrick Wilson. “I play a very dark person, which is out of my wheelhouse,” said Heigl. She also plans to start filming “A Moment to Remember” in June, which is about a fashion designer who is stricken with a disease that wipes out her memory. Heigl attended a few shows during fashion week, including Reem Acra, which she called “unreal,” and Jenny Packham, which she said was “magical. It was so Grace Kelly and so princess-inspired,” said Heigl. Others in J.Mendel’s front row were Jena Malone and Jessica Hart.