Melania Trump is proving to the fashion designers who said they wouldn’t help her that dressing well is the best revenge. The first lady’s trip to Saudi Arabia, the Vatican, Belgium and Sicily — wearing mostly Dolce & Gabbana — was a fashion tour de force that has forced many naysayers in the rag trade to rethink. The list of designers who said they wouldn’t dress Melania is long, led by Tom Ford, Marc Jacobs, Zac Posen, Christian Siriano and Sophie Theallet. But Melania has managed to look smashing in dozens of different ensembles, from her white Ralph Lauren jumpsuit...