"Director Petraeus' frank and forthright letter of resignation stands on its own," said the official, who spoke on the condition of anonymity because of the sensitivity of the topic. "Any suggestion that his departure has anything to do with criticism about Benghazi is completely baseless."
Broadwell spent a year with Petraeus in Afghanistan interviewing him for the book she co-wrote, "All In: The Education of General David Petraeus."
His resignation Friday appeared to be an abrupt end to a spectacularly successful career in public service.
"After being married for over 37 years, I showed extremely poor judgment by engaging in an extramarital affair. Such behavior is unacceptable, both as a husband and as the leader of an organization such as ours," Petraeus said in a letter to colleagues, explaining his decision to step down.
Before his nomination as CIA director, Petraeus was considered the nation's most well-known and popular military leader since Colin Powell.
He helped turn the tide against insurgents while commanding forces in Iraq and Afghanistan and literally wrote the book on counterinsurgency techniques by overseeing the development of the Army/Marine Corps Counterinsurgency Manual.
Earning praise from both sides of the political aisle, the retired four-star general took the helm of the CIA in September 2011.
Petraeus, 60, and his wife, Holly, live in Virginia. They have two adult children.