Sabé is the senior of Queen Amidala's royal handmaidens and her primary decoy, played by Keira Knightley in The Phantom Menace (1999). For much of the film's middle act she is the one wearing the ceremonial makeup and issuing the orders while Padmé Amidala moves through Tatooine and Coruscant as an apparent servant.
The trick the film plays on you
The decoy is set up in the first act and paid off in the third, when the woman the Trade Federation has spent the film negotiating with turns out to be a handmaiden and the girl in the corner draws a blaster. It is a genuine piece of misdirection, and it works because Knightley and Natalie Portman were cast for a resemblance strong enough to survive the same makeup.
Not just a body double
StarWars.com's own guide to the handmaidens calls Sabé the most well known of them "given her prominent status as the decoy queen", and the security arrangement is real rather than cosmetic: the handmaidens are trained bodyguards. Several of them fight in the Battle of Naboo.
Queen's Shadow
E. K. Johnston's Queen's Shadow (Disney–Lucasfilm Press, 2019) is the book that finally makes the handmaidens characters rather than a device. It follows Padmé from the end of her reign into her first term as senator, and Sabé is its second lead — a woman who has spent four years being someone else and has to work out what she is when the job ends. It is the best treatment the Naboo material has had in any medium.
After Padmé
Johnston's follow-ups and the wider canon material take Sabé onward into work on Tatooine and into the orbit of the surviving Naboo loyalists. The through-line is consistent: the decoy outlives the queen and keeps working.
Continuity
Canon. The Legends continuity had its own, much thinner version of the handmaidens, largely from reference books and the Star Wars: Republic comics; Queen's Shadow supersedes it.
