There is a moment toward the end of the “Devil Wears Prada 2” when the icy, imperious fashion editor Miranda Priestly, played by the incomparable Meryl Streep, suddenly softens and delight dances behind her eyes. Speaking to Andy Sachs, the film’s heroine, she muses about the diabolical reputation she’s earned and the time with her children she’s missed. But then she says, with relish: “Boy, I love working. I really do. Don’t you?”