On Friday afternoon, General David Petraeus announced his resignation as CIA director, citing an extramarital affair. Almost immediately, Slate named Petraeus’s biographer, Paula Broadwell, as the mystery woman. And according to NBC, the FBI has been investigating Broadwell out of concern that she had access to confidential information.

Broadwell is the author, with Vernon Loeb, of All In: The Education of General David Petraeus, a glowing 400-page biography of Petraeus, for which she was granted almost total access. After it was published in January, some said it read more like a love letter to the general than a biography. In a review for Rolling Stone, Michael Hastings called the book “a work of fan fiction so fawning that not even Max Boot—a Petraeus buddy and Pentagon sock puppet—could bring himself to rave about it.”

Broadwell, 40, is a research associate at Harvard’s Center for Public Leadership–as well as a PhD. candidate in the department of war studies at King’s College in London. She is married to Scott Broadwell, an interventional radiologist. They live in the upper middle class Dilworth neighborhood of Charlotte, N.C., with their two sons, Landon and Lucien. She grew up in North Dakota, and attended West Point, the general’s alma mater, where she graduated with honors. She has worked for the U.S. Special Operations Command and an FBI joint terrorism task force. Beyond that, her list of accomplishments is long: she earned an MA from The University of Denver’s Korbel School of International Studies; an MPA from Harvard’s John F. Kennedy School of Government, and served as the deputy director of the Jebsen Center for Counter-Terrorism Studies at the Fletcher School at Tufts.

Physically, Broadwell is tall and stunning, with long dark hair and green eyes. According to her biography, she has been a “sponsored ½ Ironman triathlete” as well as a “female model/ demonstrator” for KRISS, a manufacturer of .45-caliber machine guns. (On LinkedIn, she lists her current employer as Equipe Broadwell, LLC, seemingly a part of the Carolinas Freedom Foundation, a veteran’s organization in Charlotte.

Broadwell first crossed paths with Petraeus in 2006, when he gave a lecture at Harvard’s Kennedy School of Government, where she was pursuing her master’s degree. According to the preface of All In, she introduced herself after that lecture and told him about her academic research. He gave her his business card and offered to help. “I took full advantage of his open-door policy to seek insight and share perspectives,” she writes in the book. And so began an alleged relationship, which, if sources are to be believed, eventually led to the general’s resignation from the CIA on Friday.

With access to Petraeus, Broadwell decided to structure her dissertation around a case study of his leadership. She called it “a study in transformational leadership and organizational innovation influenced by U.S. Army General David Petraeus.” In July 2010, when the general was put in command of Afghanistan, Broadwell parlayed her project into a book deal with Penguin Press, and brought in The Washington Post’s Vernon Loeb to help report on the ground.

It was then that she “shot [Petraeus] an email and said ‘I’m going to go for it,’” she told Stewart. “I’m not sure he took me seriously, but I showed up in Afghanistan.” She embedded there until summer 2011, where she reported on the front lines, observed him closely, and interviewed several crucial members of his command.

Biographers sometimes develop obsessions with their subjects. And, in hindsight, it is peculiar that Broadwell repeatedly referred to Petraeus as a mentor—saying in an interview that he approached her project “from a mentoring point of view.” In All In, she writes that he saw her as an “aspiring soldier-scholar.” In an interview with Jon Stewart, she sounds adoring of Petraeus. “He can turn water into bottled water,” she joked. In that interview, she explains that Petraeus’s high-school nickname—which has apparently stuck with him since—was “Peaches.” (After her book tour in January, she was reportedly going back to finish her doctorate—where, she told The Charlotte Observer, Petraeus was also one of her dissertation advisers.)

Like Petraeus, Broadwell is an avid athlete. At West Point, she ran cross-country and track—and graduated at the top of her class for physical fitness. In an online bio, she describes her hobbies as running, skiing, and surfing. When she appeared on The Daily Show in January—she challenged Stewart to a push-up contest for charity, which she easily won.

Broadwell got to know Petraeus through several five-mile runs that doubled as interviews—a tactic he’s been known to use with journalists. “It was an opportunity for me to interview him on a run,” she told Stewart. “I thought I’d test him, but he was going to test me—it ended up being a test for both of us since we both ran pretty quickly. That was the foundation of our relationship.” When he didn’t want to answer questions, she said, “He would pick up the pace so neither of us could talk.”

Just last week, Broadwell documented Petraeus’s “Rules for Living” in Newsweek—which read like the 12 commandments for military leadership and personal excellence. The fifth rule, smack in the middle, states simply, “We all will make mistakes. The key is to recognize them and admit them, to learn from them, and to take off the rearview mirrors—drive on and avoid making them again.”