1) How to Marry a Millionaire (1953)
If there's anything more stylish than a Marilyn Monroe movie, it's a Marilyn Monroe movie that co-stars Lauren Bacall and Betty Grable. The powerhouse trio is impossibly chic throughout this film. Plus, Monroe makes a reference to a character being in Harper's Bazaar three times as an indicator of her class, so you know it must be good.
2) High Society (1956)