To hear Mary (Ella Bruccoleri) tell it, she is no one special. She is not “the beautiful one” of her sisters, nor “the quick-witted one,” and she is certainly not “the ones who are good at games and full of youthful energy.” If she is anything, she is the odd duck, seemingly doomed to a future of getting overlooked by suitors and dismissed by her family.

It is both ironic and entirely appropriate, then, that this very ordinariness is precisely what makes her such a striking heroine in The Other Bennet Sister , BritBox ’s wildly charming effort to reframe the resident frump of Pride & Prejudice .…