The medal is Spendolini-Sirieix’s first individual medal at the World Championships and follows her gold in the team event on Saturday.
The teenager and Lois Toulson became the first British women to win a world diving medal when they secured silver in the 10m synchronised event last year.
Toulson finished sixth in Monday’s individual final with gold won by China’s Olympic champion Quan Hongchan and silver taken by her compatriot Chen Yuxi, the defending world champion.
Quan and Chen dominated the competition by finishing on 436.25 and 427.80 respectively with Spendolini-Sirieix, the daughter of French maitre d’ and TV personality Fred Sirieix, third with a score of 377.10.
Thorpe and Shortman, whose routine was inspired by London landmark Big Ben, finished second behind China’s Wang Liuyi and Wang Qianyi, with Spain’s Alisa Ozhogina and Iris Tio claiming bronze.
“It means so much, I can’t even put it into words,” said Thorpe. “I just hope it’s inspiring some young girls and boys back at home, and we can lead the way for some of them and that there’s a bright future for artistic swimming in the UK.”
Shortman added: “Hopefully we can get a bit more publicity for the sport now and we can encourage people to get involved, everything that comes with it.”
Last July, Shortman made history by taking bronze in the solo free final at the 2023 World Championships in Japan.
Thorpe and Shortman are in action again on Wednesday in the preliminary round of the free duet event, with the final held on Friday.
Scores from both finals are combined for deciding qualification for this summer’s Paris Olympics.