Jill Kelley, who prompted the investigation after complaining of harassing emails that turned out to be from Mr Petraeus's mistress, Paula Broadwell, is understood to have asked the FBI to drop it in the summer.
News of her change of heart came as it emerged that Mrs Kelley, a "social liaison" for the US military, made repeated calls to the police this week asking them to remove journalists from outside her house.
Wielding a title given to her by the South Korean government, she told dispatchers: "I'm an honorary consul general, so I have inviolability."
She added: I don't know if you want to get diplomatic protection involved as well."
Sources close to the FBI told press that Mrs Kelley, a 37-year-old mother of three, tried to withdraw her complaint after growing "worried about the personal information being provided".
She may have been anxious to protect members of America's military and political elite to whom she remained close up until the moment she was named as "the other woman" in the Petraeus saga. As her name was made public on Sunday, Mrs Kelley was entertaining a group including the current deputy commander at US Central Command, Vice Adml Robert Harward, at her Tampa mansion.
It also emerged in court documents that Mrs Kelley's brother-in-law was employed as a "consultant" by a private intelligence firm that carries out work for US intelligence agencies. Working as an operative for EWA ITT, Grayson Wolfe, who is now estranged from Mrs Kelley's twin sister Natalie, travelled frequently to Pakistan and took his wife to the Middle East in 2008, while Gen Petraeus was leading the war in Iraq.