Queen Amidala's Decoy was an NPC, one of Queen Padme Amidala's handmaidens, who regularly disguised herself as the Queen to protect her.
The Phantasmal Malevalence[]
When the Trade Federation's first invasion of Naboo began, Padme and her decoy managed to trade places disguised as each other, when they were captured by the Feds' droids along with Sio Bibble, Panaka, and a group of handmaidens, Padme among them. The group was being forcibly escorted by the droids to the palace courtyard when they were rescued by the Jedi Qui-Gon and Obi-Wan.
When the Jedi learned from Bibble that Senator Palpatine on Planet Coruscant had information on the Lost Orb of Phanastacoria, they and Jar Jar Binks wanted to go there right away. When the decoy tried to insist that the Jedi should stay and try to defend Naboo, Qui-Gon offered to take her along with them. Panaka refused to let her leave without them, so Qui-Gon agreed to take the Queen's entire entourage except for Bibble, whom Qui-Gon distrusted.
Paadme's decoy and the others managed to escape on the royal barge, flying it into orbit, trying to get the ship past the Federation blockade.
As the royal barge tried to fly through the Federation blockade, the Feds opened fire on the ship, severely damaging it's shield generator. One more hit would've been enough to destroy the ship. R2-D2 volunteered to go out on the hull to fix the damage. There were a few other astromech droids on the hull working on it, but they were blasted away by the Feds firing on them. R2 was able to fix the generator, restoring the shields, and the ship was able to fly through the blockade to safety.
Ric Olie reproted the ship was 23% damaged, but would be able to make it to Coruscant. Obi-Wan thought they should stop at the nearest planet for repairs. Qui-Gon agreed, and also wanted to add weapons to the ship, in case the Feds pursued. They headed to the nearest planet, Tatooine, a desert wasteland ruled by gangsters.
The false Queen sent for Qui-Gon, Obi-Wan, and R2 to thank them for saving the ship. Obi-Wan tried to talk her into landing on Tatooine. The false Queen allowed them one day on Tatooine to get the repairs and weapons they wanted. R2 demanded, in exchange for saving the ship, that the Queen have her most beautiful handmaiden polish him. The Queen acceeded to R2's request by sending him her handmaiden, Padme.
When the ship landed outside a major city on Tatooine, Obi-Wan decided to stay on the ship feeling the need to proctect the Queen from any encounter they might have with sand creatures.
As Qui-Gon, Jar Jar, and R2 left the ship, Panaka told them the Queen had ordered them to take Padme with them to learn more about the planet.
The false Queen stayed on the ship the entire time they were on Tatooine along with Obi-Wan and the rest of the Queen's entourage. When they got the repairs and weapons for the ship they wanted, they were able to fly to Coruscant without incident. While there, the false Queen apparently traded places with Padme as the Queen went to address the Senate. They traded places again after the ship left Coruscant and headed back to Naboo.
On the way back to Naboo, the Queen (back to being the decoy again) asked Qui-Gon what his plan was. Qui-Gon started off with a plan that rehashed how this story all started. When Obi-Wan pointed this out, Qui-Gon put Jar Jar in charge. Jar Jar proposed the Naboo humans should unite with the Gungans to form a big army to liberate Naboo from the Feds.
As the ship reached Naboo, R2 wanted to attack the Feds' orbital hq, but Jar Jar vetoed that idea since the hq had the Orb protecting them. He ordered the ship to land near Otoh Gunga.
Everyone gathered around the shore leading to the underwater city of Otoh Gunga, waiting for Jar Jar to return from there and give a report. He arrived and reported that the Gungans had all left the city to go to the secret hiding place in the swamp, to make exlopding soap bubbles for the fight filled with electric mosquitoes, and that these bubbles would be piled on the backs of the dinosaur ponies.
Jar Jar led them to the hiding place, where they met the Gungans headed by Boss Nass and Captain Tarpals. The Queen appealed to the Gungans for aid, but was refused by Nass. She asked Jar Jar to negotiate. Jar Jar told Nass that they should help the Naboo humans defeat the Trade Federation droids, and then they could retrieve the Lost Orb of Phanastacoria. Nass agreed, but Jar Jar insisted he should demand payment for their aid: 10 humans per day so the Gungans would never have to worry about food again. At this point, Padme came forward to reveal that she, Padme Amidala was the real Queen of Naboo. She offered to sacrifice herself to the Gungans to save her people. Fortunately, Anakin came up with a better solution. He pointed out to Nass that without their help, the Gungans couldn't get to the Trade Federation orbital headquarters where the Orb was, and it'd be a shame if someone should destroy the hq and the Orb along with it. Nass backed down, and agreed to help the humans.
Everyone made their strategy. Jar Jar would lead the Gungans to fight the droid army by attacking them with the soap bubbles. Qui-Gon suggested they fill up the bubbles with water from the geysers at high tide. Meanwhile, everyone else would storm the palace through the hangar and take the Fed leaders captive.
Nothing more was seen of Queen Amidala's loyal decoy after this.
A New Generation[]
If the unnamed loyal decoy of Queen Amidala was still alive 32 years later, and still living on the planet Naboo, then she was most likely killed along with everyone else on Naboo when Darth Vader ordered the planet's destruction from the laser of the Peace Moon.