We watched this on BFI Player, where its English title was the direct translation of the French one: My Girlfriend’s Boyfriend. But Letterboxd knows it as Boyfriends and Girlfriends. The French title is both better and more accurate, and the potentially-ambiguous meaning of ‘amie’ is matched by that of ‘girlfriend’ when used by women.
Anyway, another of Eric Rohmer’s excellent gentle comedies. And why not?