It was that same website where I found the quote from the program, but I was wrong about the timing -- because it was the Timespace tour book. So apparently she first explained on the Timespace album that the song was written for Joe, and then said it again on the program. I think I must have read something on a message board somewhere that somebody first saw that information on that program. The quote from the program as they have it on Seven Wonders:
"He had written a song for his baby that he had lost, and I wrote a song for the both of them. My life changed that day. I told the public it was theirs and mine, but it never was, it was my Joe's song, and I would never, ever be the same..."
~Stevie Nicks, Timespace tourbook, 1991
Also the words she quotes from her song right after that, made me wonder if she was telling him something, again, just like in the mid-80s, where she had been telling him he wasn't "finished." Beginning with "Thank you, Joe," and going on to quote from her song with "If not for me, do it for the world," and wrapping up with the word "LEGEND" in capital letters . . . that was a very personal statement to him, I thought.