The Paris prosecutor's office and did not respond to a request for confirmation of Arnould's written remarks on Instagram.
Lawyers for Arnould and Depardieu did not immediately reply to a request for comment.
Depardieu, one of France's leading film stars whose reputation has been tarnished by multiple sexual assault allegations, has denied wrongdoing in the case.
Arnould, 29, an actor and former ballet dancer known for her work in theatre and voice acting, publicly accused Depardieu of rape in 2018, alleging the assaults occurred when she was in her early 20s.
Though her case was initially dropped, it was reopened in 2020 and investigative magistrates placed Depardieu under formal investigation in 2022.
"I think I'm having trouble realising how huge this is. I'm relieved," Arnould wrote on Instagram.
Arnould has alleged the assaults occurred at Depardieu's Paris home on two occasions.
She has become a vocal figure in France's #MeToo movement, expressing solidarity with other sexual assault victims and demanding accountability in the film industry.
Depardieu, 76, who has starred in scores of French-language movies, rising to prominence in 1974 with Going Places, has been at the centre of a growing number of sexual assault allegations in recent years.
Arnould was present in the courtroom in May when Depardieu was found guilty in a separate case of sexually assaulting two women on a film set and handed an 18-month suspended prison sentence.
During that trial, Depardieu's lawyer called her a liar in the courtroom.
In her Instagram post on Tuesday, Arnould referred to those comments, calling Depardieu's defence "outrageous and ... absolutely unnecessary to uncover the truth".
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