Laure clocked 2:08.06 to win the 200 metres backstroke title and clinch a second berth at the Olympics, after the 100 backstroke.
She qualified along with Alexianne Castel who finished second in 2:08.57.
Laure, the 400 champion in Athens in 2004, was 0.28 seconds slower than third-placed Dutchwoman Sharon van Rouwendaal's 2:07.78 at last year's world championships in Shanghai.
"I know what I have to do now and I will have to swim faster if I want to grab an Olympic medal," Laure said.
She will travel to London with younger brother Florent who qualified after finishing second in the 50 freestyle.
Amaury Leveaux, Olympic silver medallist in Beijing in 2008, won the race in 21.93 seconds.
Florent, who clocked the third best time in the world this year in Friday's semi-finals, was second in 21.95.
Laure's boyfriend Frederick Bousquet, world silver medallist in 2009, could only finish fourth.
Alain Bernard missed out with his last chance to earn an individual Olympic spot when he was fifth in 22.15.
Bernard, 100 freestyle champion in Beijing, had already failed to qualify in the 100 and will only take part in the relay in London.
"It's the beginning of the end. I worked very hard but I did not swim the way I wanted," said the 28-year-old Bernard after receiving a standing ovation from the crowd.
"The ovation was beautiful. The competition ruled today, that's what sport is."
Coralie Balmy also booked her ticket for the Olympics by winning the 800 freestyle in 8:29.96.
The Games start on July 27.
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