I suggest your friend to watch this:

Ayumi Hamasaki - The Face on Every Billboard
http://www.youtube.com/watch?v=t_RjkyoZ9cM

Ayu writes ALL of her songs. She's been doing it since her first single. And Ayu is in control of everything she does. I remember that Max Matsuura said that when the CDs say produced by Max Matsuura, it's only because of the contract he signed and that he really doesn't do anything. It's Ayu herself. (She's a bit of a control freak)