"Parabens para voce!" -- the traditional Brazilian birthday song that mirrors the "Happy Birthday to You" tune in English -- greeted Bruni as she visited the Pavao-Pavaozinho favela above Rio de Janeiro.
And in a nod to Bruni's modeling days, a dozen pretty dark-skinned women from the slum paraded in front of her for a local fashion show put on by a Franco-Brazilian charity.
Bruni took in the show under an umbrella to protect her from the burning tropical sun, while a young girl sat on her knees.
"She mainly commented on the texture of the garments -- the recycled plastic and the bamboo, and how light they were. Her presence was very important, and we hope that will raise our profile," said Nadine Gonzalez, the founder of the Modafusion initiative specializing in environmentally friendly fashion.
One of the models, 20-year-old Etieni, said she was "lucky" to step up onto the catwalk in front of such a famous person "because the competition is tough in the modeling agencies."
Etieni's mother, Ana, said she was grateful to the charity for "allowing her daughter not to fall into another life" -- prostitution.
"This year, she's going to university," she said, her pride apparent.
Bruni, sporting a dark violet suit with short sleeves and low-heeled moccasins, had a look at another charity before the fashion show.
That project, Crianca Esperanza, is backed by UNESCO and Brazil's top private television network Globo. It aims to lift 8,000 poor children out of misery and turn them away from the life of drug trafficking and abuse that awaits so many born into Brazil's underclass.
Around 50 children welcomed France's first lady with another rendition of "Parabens para voce" and a bouquet of flowers.