Could Trump have lied to her about that too? And therefore the statement isn't knowingly false?
I'm just trying to figure out what would cause this woman to write and sign that statement to the FBI.
Maybe.
Her certification was in the passive voice: “Based upon the information that has been provided to me, I am authorized to certify, on behalf of the Office of Donald J. Trump, the following: a. A diligent search was conducted of the boxes that were moved from the White House to Florida; b. This search was conducted after receipt of the subpoena, in order to locate any and all documents that are responsive to the subpoena; c. Any and all responsive documents accompany this certification.”
She doesn't say who conducted the search or who told her the results. But if she claims she was relying on someone else's representations,
she'll have to say who. If it was Trump, that doesn't seem great for his own criminal liability exposure.