Najila Trindade Mendes de Souza has accused the football megastar of raping her in a Paris hotel in May, a charge which he denies.
Trindade arrived at the Sao Paulo police station at midday, her face covered by a black jacket as she was escorted by officers through a media scrum outside.
She emerged after six hours of testimony, which the UOL website said was videotaped in a room with three female police officers present.
Trindade was carried out of the police station in her lawyer's arms, and did not speak to journalists.
Her dramatic appearance came a day after Neymar went to a Rio de Janeiro police station -- sitting in a wheelchair after injuring his ankle in Wednesday's pre-Copa America friendly against Qatar.
He gave a statement in an investigation into his publication of intimate WhatsApp messages and photos of Trindade on social media without her consent.
Neymar told police that an assistant and a technician were responsible for sharing the messages and photos, TV Globo reported.
In the latest twist in the drama dominating headlines and conversations in Brazil, previously unseen WhatsApp messages allegedly between the pair were broadcast Thursday by TV Globo and Record.
These exchanges -- dated May 16, a day after Trindade said she was raped -- featured a photo of Trindade's buttocks covered with bruises. Neymar wrote: "For these marks you are also guilty, ha ha ha, you asked for more."
Trindade replied: "You are mad, I asked you to stop and you even apologized!"
In extracts of an interview with SBT TV network aired shortly before Wednesday's game, Trindade described suffering "aggression together with rape" at the hands of the player.
Neymar lasted 20 minutes in the game before spraining his right ankle that has sidelined him from the tournament and put his playing future with Paris Saint-Germain and Brazil in doubt.
More than 60 percent of Brazilians believe Neymar is innocent, according to a poll of 2,071 Brazilians this week.
Only 14 percent think he is guilty, Parana Pesquisas said Friday.