So the most logical explanation is that her staffers prepped her for the debate using language taken directly from the Goldberg/Ambinder article, whether or not she had been briefed on the threat to Pakistan’s nukes originally.
All that said, such an obvious explanation begs the question of why Ambinder’s colleague, Yochi Dreazen,
had this to say in a fact check of Bachmann’s comment.
During the CNN debate, Bachmann said that 15 Pakistani nuclear sites were vulnerable to jihadist attacks, and that six of the sites had previously come under some form of Islamist attack. U.S. intelligence and military officials believe that Pakistan has 15 nuclear sites, but no U.S. official has publicly said that all of the sites were vulnerable to militant attack or confirmed that any of them had previously come under any form of jihadist attack.
Sure, no US official has publicly said that all the sites are vulnerable or that 6 had come under attack. But the National Journal (in partnership with the Atlantic) has said it, presumably based on the anonymous leaking of at least one US official. And why suggest Bachmann’s statement was inaccurate when NJ itself had first published the information?
Taking the NJ’s comments together, we ought to assume Bachmann’s comment was, generally, accurate, but the NJ doesn’t want to take responsibility for having published what Bachmann has now magnified by using it as a debate zinger.