It's not that she's shy. In fact, Valerie Trierweiler is known at the magazine Paris Match, where she works as a journalist, for slapping a male colleague who made a sexist remark.
She also managed to win presidential hopeful Francois Hollande away from his partner of 30 years and the mother of his four children, Segolene Royal.
Hollande relaxed on last campaign day
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Hollande relaxed on last campaign day
Footage of French presidential candidate Francois Hollande has he goes to market the day before the people go to the polls.
And she lashed out publicly when her own magazine featured her and Mr Hollande on its cover last month. "I am angry to see the use of photos without my agreement and without letting me know," she posted on Twitter.
She followed up with congratulations to the magazine on having reduced her to a trophy partner "on International Women's Day … (spare) a thought for all angry women".
Assertiveness notwithstanding, Ms Trierweiler, 46 and a twice-divorced mother of three, will be a reluctant first lady of France if the voting in the election starting today results, as polls predict, in Mr Hollande becoming president.
She might not in any way fill the ballet slippers of glamorous Carla Bruni, the wife of current President Nicolas Sarkozy (Ms Bruni, a former supermodel, always wears flat shoes because she is 10 centimetres taller than her husband).
While she has sometimes accompanied Mr Hollande to political events, Ms Trierweiler stays in the background. She declines to be interviewed and journalists have been told they are not "campaigning as a couple". The press does not call her Mr Hollande's "partner" but his "companion".
Nor is there any serious talk of marriage, despite the historic French preference for married presidents.
Asked during the campaign if he intended to marry her if he won, Mr Hollande said, "You do not get married just for reasons of protocol. You get married out of choice. "I stand alone as a candidate before the French people. Alone. It is not a couple standing but a personality who must convince with his ideas, his method … I will do nothing which is against my principles."
All of which makes this relationship an interesting milestone in the evolution of French attitudes to the sex lives of politicians.
The French have long tut-tutted over what they saw as adolescent Anglo prurience in the obsession of British tabloids, for example, with the love lives of the rich and famous. Traditionally, French politicians were allowed to keep their peccadilloes off stage as long as they were managed discreetly. Paris Match revealed during his time in office that then president Francois Mitterrand had a mistress and a love child but the rest of the French media ignored the story.
The custom largely protected male indiscretions.
But there has been more publicity over Ms Trierweiler. Mr Hollande's separation from Ms Royal was announced just after the 2007 election in which Ms Royal, also a senior Socialist, had lost her own bid to be president.
A few months later, a French website published news of his romance with Ms Trierweiler, which had begun when she interviewed him in 2005 in a meeting she later described as "a lightning strike".
Since then, Mr Sarkozy's flamboyant love life has grabbed the headlines. In 2008, he married Ms Bruni, 12 years his junior and with a colourful past of her own that included affairs with Mick Jagger and Eric Clapton, less than four months after divorcing his second wife.
The courtship was public, including kisses at the Great Pyramid of Giza and press conferences in which Mr Sarkozy meditated upon love and destiny, offending traditionalists who criticised it as American-style tabloidisation of French politics.
Ms Bruni, who is also a singer-songwriter, has also discomfited the French with confessional lyrics about falling in love with her husband, and about her indifference to public criticism: "Let them curse me and damn me/I don't care."
If anyone has broken the mould of France's (unofficial) first lady, it is Ms Bruni.
For Ms Treiweiler, the attempts at distance from Mr Hollande's public life have not been enough to protect her career as a political journalist from problems with conflict of interest. She had to stop attending editorial conferences at Paris Match during the campaign, saying, "They cannot deprive themselves of a subject and I cannot intervene." She also recently gave up presenting a TV show called Portraits of Candidates for another on celebrities.
If the last Ipsos opinion poll taken before campaigning ended on Friday night is to be believed, Ms Bruni will soon be exiting the Elysee. It found Mr Sarkozy was narrowing the gap but still trailing Mr Hollande, 47.5 per cent to 52.5 per cent. The poll was taken before defeated centrist candidate Franç¸ois Bayrou told voters to back Mr Hollande.
Ms Bruni last year told the BBC that when she stopped being first lady, she would "just go back to touring, you know. Playing guitar and touring is what I miss the most''.
And her husband? "He's going to work until he dies. He's that type of man … After taking care of France in the way he did it, I think you can do absolutely any other job."