It could be this but she said something about finally joining Minato when she was disappearing.Perhaps Minato and herself where talking about the insidant in purgatory.
Lol your sigYou must be registered for see images
OT: I would say just Kishi taking liberties with these falshbacks.
Listen to this guy ^^^You don't understand what actually happened. Same way that Minato was aware of his son's life during his "meeting' with him during the Pain invasion. The chkra somehow witnessed all of it, and recorded for Minato and Kushina. He did it that way on purpose. I have no clue how it works, obviously, but it was explained.
also this comment is pretty accurate I think.I don't thhink she really told him how Minato and and the masked man fought. All the action was for the viewers. Maybe all she told Naruto was that Minato fought the masked man and the kyuubi was in the village.