Aline Brosh McKenna always seemed aware that writing a sequel to The Devil Wears Prada would be a dangerously narrow runway to walk. That’s probably why, as recently as three years ago, she wasn’t particularly keen on the idea. But when Meryl Streep says she’s thinking about revisiting one of her most famous roles, what’s a screenwriter to do? It took 20 years after they released one of the most impactful comedies of the 21st century to get the entire band back together. But, as McKenna says, once she met with Streep… things moved very quickly. “Meryl’s opinion is enormously important,” says McKenna, whose other credits include 27 Dresses, Morning Glory, We Bought a Zoo and Crazy Ex-Girlfriend .…