Flanker Oscar Jegou and lock Hugo Auradou were detained in Buenos Aires on Monday having played in Les Bleus' tour-opening win over Argentina in Mendoza on Saturday, where the supposed attack took place.
The alleged victim's lawyer, Natacha Romano, told local Mendoza media her client had been "savagely beaten" during the attack, with visible injuries to her face, head, ribs and legs.
Jegou, 21, and Auradou, 20, risk a sentence ranging from six to 15 years for sexual assault, according to the Argentine penal code, however this could go up to 20 years in the case of two aggressors.
"It was a difficult moment to manage emotionally," scrum-half Couilloud told reporters.
"We thought only of what was happening on the field today, and it's the only thing that keeps us going with this tour."
They are set to be transferred to the western city of Mendoza before they undergo questioning and forensic examination, as 26 members of the original 42-man squad headed to the Uruguayan capital for the midweek game.
Full-back Melvyn Jaminet was also missing from the match after being removed from the squad for making racist comments on social media.
France head coach Fabien Galthie named a hugely inexperienced side to face Los Teros, with 14 members of the 23-man side uncapped at international level.
Couilloud and replacement lock Posolo Tuilagi's doubles were the key to Les Bleus' victory.
Hooker German Kessler, centre Felipe Arcos Perez and replacement Guillermo Pujadas scored consolation efforts for the home side and they were awarded a late penalty try.
France end their end-of-season South America tour with a second Test against Argentina on Saturday in Buenos Aires.
