I think what she is saying is that her lawyer doesnt believe it to be the sort of material that would be covered by the official secrets act. But as CirrusF pointed out that is not always obvious. How would he know, you might well ask?
What he would know however is what a UK court is likely to make of it, and the UK courts don't take too kindly to being told that they can't deal with the simple facts, particularly because another country says they can't.
Since this took place inside Nato headquarters, he appears to have been having an authorised meeting, what was he authorised to tell her and how was that authorisation given? We dont know. The hang him high merchants need to rein their necks in, not least because if he's been arrested and charged the normal rules apply.