It would make a lot of sense of a reporter preparing a book to make every possible effort to bypass other news media, and Administration statements and try to get directly to the folks in the CIA putting together the reports the Administration was using.
Judith can't recall WHO because there are many folks who provided her information for her book.
IMHO Judith Miller can't recall, for exactly the same reason the Clinton twins could not recall. Taking the fifth makes everyone more suspicious.
Little does Judith realize that post-Clinton, can't recall, raises the same suspicions.