“Why shouldn’t films look like this?” asks director Emerald Fennell, who believes diverse storytelling doesn’t just open the door to different stories and characters, but a diversity of craft. In talking about the colorful world she built around Cassie (Carrie Mulligan), Fennell breaks down how she constructed a film that tackles difficult issues in such entertaining and subversive ways. At the 24 minute mark, Emerald and I welcome “Promising Young Woman” costume designer Nancy Steiner and production designer Michael Perry to the conversation, where we talk about everything from Paris Hilton Videos to Twin Peaks to Sweet Valley High.