Mimi Marchand, who runs the BestImage agency, had also been charged with criminal association, said lawyer Caroline Toby. “She firmly denies the charges against her,” she added.
Marchand was arrested on Thursday along with several other suspects on the orders of magistrates investigating alleged corruption by Sarkozy, who has been accused of taking money from former Libyan dictator Moamer Kadhafi.
Sarkozy denies the charges.
Francois de Labarre, a journalist from Paris Match who was also arrested Thursday, was released without charge later the same day.
Marchand and de Labarre were instrumental in organising an interview in November with one of the main witnesses against Sarkozy, Ziad Takieddine, in which he withdrew his allegations against the former head of state.
Afterwards, speaking to French investigators, Takieddine changed his story again, retracting what he had told Paris Match and saying his words had been “deformed”.
Marchand’s lawyer Toby insisted Saturday that her client had “acted in her capacity as a journalist who had this exclusive interview with Takieddine.
“All she did was organise the photos and the interview, within the parameters of her job,” she added.
Marchand, known widely as “Mimi”, works closely with a host of rich and powerful figures from the worlds of politics and entertainment, including President Emmanuel Macron and his wife Brigitte.
The investigative website Mediapart, which first reported the detention of Marchand and de Laberre, said they were suspected of “underground negotiations with Mr Takieddine” to convince him to withdraw his allegations against Sarkozy.
Before retracting his claims in the Paris Match interview, Takieddine had always alleged that he delivered suitcases stuffed with five million euros ($6 million) in cash from Tripoli to Sarkozy’s chief of staff in 2006 and 2007.
Marchand’s arrest is the latest twist in years of extraordinary claims and investigations against pugnacious right-winger Sarkozy, who served one term as president, from 2007-2012.
In March, Sarkozy was found guilty of influence-peddling and handed a three-year prison sentence for attempting to influence a judge to obtain information in a separate case.
Most of the sentence was suspended and he is appealing, meaning he is unlikely to go to jail, but he faces other charges including in the cash-from-Libya case.