The 22-year-old native of Geneva is suspected of seriously injuring her companion, Thomas Vergara, who suffered knife wounds to the chest, according a report from broadcaster RTL confirmed by a police source.
The incident occurred around 2.30am in a hotel in Boulogne-Billancourt, near Paris, media reports said.
Officers were called to a room in the hotel following a major dispute between the couple.
According to RTL, Benattia raised the alarm by contacting a receptionist at the hotel.
She alleged that she and her boyfriend had been attacked near the hotel by three individuals, a version of events that police officers found to be “incoherent”, newspaper Le Parisien reported online.
Benattia, referred to in French media as simply Nabilla, declared that her friend was injured while trying to defend the couple, according to the report.
However, justice official Christophe Moulin told radio station Europe 1 that she later admitted to stabbing him.
Vergara, 28, who appeared in the same reality TV show (Les anges de la téléréalité) that shot Benattia to fame, was taken to the Georges Pompidou hospital in Paris in serious condition, although his life was not threatened, RTL said.
The broadcaster said Vergara has refused to file charges against Benattia.
She had a “nervous crisis” when arrested and was briefly hospitalized before being placed in detention for a period of up to 48 hours, Le Parisien said.
Benattia already spent a month in detention as a minor for a past fraud case in Switzerland.
The petite woman, who has made no secret of her DD-sized breast implants, became a media personality and launched her own short-lived reality TV show, featuring her family, as well as a line of clothes.
But Benattia, regularly described in Swiss media as a "bimbo", has endured a love-hate relationship with the French public.
Last year she was voted the most detested person in France in a survey conducted for Voici magazine.