The seventh-grader from Creighton Middle School in Lakewood, Colo., was puzzled by "cerastes," the name for a snake commonly found in Egypt and Asia Minor.
"I had never seen that word before," said Sylvie, 12, who tried to figure out the spelling by asking the origin of the word.
She started spelling the word with an "S," stopped, asked to start over and then spelled it as "sorastes."
She was the first of the finalists to be eliminated from the bee.
Her parents, Jeff Lamontagne and Suzanne McClung, reminded her how far she has come.
This was Sylvie's first time at the national bee, but was also her last. Unlike some other regional bees, the Denver region won't send a speller to the national bee more than once.
Sylvie started participating in bees in the third grade, came in 26th place as a fifth-grader in the state bee and moved up to 8th place last year.
"If she ends up on that couch, she's still 10th in the nation," McClung said. That turned out to be the case – spellers who misspell a word are escorted off the stage to a couch where they can be comforted by a family member.
Throughout the bee, Sylvie spent every spare moment studying from a word list with her dad and her coach, Scott Isaacs, who was crowned spelling bee champion in 1989. His winning word was "spoliator."
During the semifinal and final rounds, however, spellers do not have a list to study from, and then it may come down to luck, Sylvie said.
Sylvie was tied in 9th place at the end of the semifinals, after two spellers who ranked higher than her misspelled their words.
While she was happy to advance into the final 10 spellers who were onstage Thursday night, Sylvie said she felt sad every time someone missed a word.
"I've learned a lot about how to react to another competitor getting eliminated," she said. "In other spelling bees that I've been in, the spellers didn't stand up to applaud when other spellers were eliminated."
After missing her word, Sylvie sat in the audience with her family, clapping for the other spellers and standing up in reverence to those who, like her, were eliminated from the competition.
"Often people will say that, spelling bee isn't against the other spellers; it's actually against the dictionary," she said. "Because the other spellers aren't trying to knock you out, but the words in the dictionary are."
In the championship finals round, spellers are out if they misspell any word. When either two or three spellers remain, the competition moves to a list of 25 end-of-bee words. If all or both miss in a round, all will continue. If the spellers continue to spell the words correctly, co-champions can be declared – as happened last year.
Colorado's other spelling bee competitor, Cameron Keith, did not make it to the Scripps National Spelling Bee semifinals.
Scripps is the parent company of 7NEWS, KMGH-TV & TheDenverChannel.com in Denver.