Cécile Bourgeon, 25, was charged on Tuesday with delivering the "fatal blows" to her daughter Fiona, who she had reported missing in May.
Bourgeon had been questioned during the afternoon by judges in the central city of Clermont-Ferrand, over the circumstances of how Fiona, whose body has not been found, died.
Bourgeon had already been charged last month with four offences: failing to help a person in danger, unlawfully handling a dead body, falsely reporting a crime and interfering with a crime scene, but had accused her then-partner Berkane Maklouf, 32 of beating five-year-old Fiona to death in May.
The decision to requalify the charges to include one of delivering "coups mortels agrravés" (aggravated fatal blows) was taken by the judges on the advice of prosecutors.
The former couple now appear to be pitting their testimonies against one another, and according to sources cited by Le Parisien, Maklouf and Bourgeon will ultimately testify against one another in court, but not before November.
Cécile Bourgeon elicited nationwide sympathy with her tale of how, pregnant at the time, she had fallen asleep on a park bench in May and had woken to find her little girl was gone.
The 25-year-old had issued a tearful appeal for help in finding her daughter, Fiona.
Fiona 'buried naked in a forest'
In September, Bourgeon and her former partner gave conflicting accounts of how Fiona died.
Maklouf said the child died after choking on her own vomit and that the couple panicked when they found her body in the morning.
A judicial source said Bourgeon had cracked under intensive questioning and told police that Fiona had died as a result of being hit repeatedly by her boyfriend after a heavy drinking session, and that her body had been stuffed in a leather bag, and then buried naked on the fringes of a forest.
On September 27th, about 40 police officers with three sniffer dogs were called in to scour the edge of a lake south of the central city of Clermont-Ferrand to search for the girl's body.
On Thursday, Bourgeon had attempted to lead police to the sport where Fiona was interred, but also explained that it was Maklouf himself who had physically buried her, and that her recollections were vague.
Subsequent attempts by Maklouf to lead investigators to the place where Fiona was buried, also proved futile.
On May 16th, Bourgeon appeared before French media, tearfully asking the French nation for help in finding her daughter.
“I think about everything and nothing in particular. This is very hard, psychologically," she said in a separate interview. Here is a short video of first national television appearance (in French.)
In August The Local reported how the Bourgeon had renewed her desperate appeal for help and even spoke to the media of her disappointment at the lack of solid leads in the search for her daughter.
“Three months have already passed and still no good news,” she told told regional daily La Montagne at the time. “We’re still waiting for a solid lead. It’s very hard, but I have to keep fighting,” she added.
“Where I’ve been disappointed is that there have been so many testimonies which have led nowhere. But if someone does have information, they must come forward,” Bourgeon said.
The realisation that the couple had lied for the intervening four months left those who led the search for Fiona disgusted.
“What they have done is despicable. It’s horrible, indefinable and inhuman,” Stephane Pozzo, who started a Facebook group in solidarity with Bourgeon, told Europe1 radio in September.