Well, you really gotta question the memory of an 86-year old woman. You don't know about the mental capacity of the elderly, most of them get kind of vague and forgetful, and they seem really easy to persuade and more likely to accept suggestions not really in their best interests. I know some little old ladies are sharp as a tack, but...
Forget the elderly....I'm less than half her age and have probably written thousands of memos on related subjects. No way could I relate with any detail "what" was in a memo 15 years ago....but she recalls 40 years ago?