The canoe slalomist stormed to victory in the women's kayak single at the Lee Valley White Water Centre, finally putting to bed the suspicion that she lacked the mental fortitude to go with her obvious talent for paddling.
"Between the semi-final and the final I put my iPhone very loud and I danced," said the 29-year-old who is coached by her long-term boyfriend Sylvain Curinier.
It worked a treat as she produced a superb final run to beat Australia's world junior champion Jessica Fox to gold by 0.36 seconds, completing a fabulous 48 hours for France at the Lee Valley complex situated just north of London after Tony Estanguet claimed a third Olympic C1 gold medal on Tuesday.
Spain's Maialen Chourraut finished third.
In Beijing, Fer was one of the favourites to take gold but managed seventh place.
Until Thursday the daughter of former French champion Gaelle Madrange had never won a major international individual honour with fourth at last year's world championships in Slovakia her most notable achievement.
Curinier showed faith in her as many questioned whether she had the mental strength to win one of the sport's major prizes.
"People have always said she didn't have the mentality but I always believed that it wasn't true. I always believed she was foundering for other reasons", he told Reuters.
Asked what had turned her into an Olympic champion she said she had taken a good look at herself.
"After Beijing, I knew I had to dig deep into my spirit," she told reporters, adding she had worked with a sports psychologist. "I learned a lot of new things that I'm now using when I compete."
"I've still had lots of ups and downs. But the ups were telling me that one day I would be able to achieve great things. And when I got downs, I was really well prepared.
"I've learned, that when I'm competing, I have to control my emotions and be cold, which is a bit strange because I'm not like that in my daily life. I discovered myself."