Hilary Duff is coming clean about what inspired her return to music with her new song, "Mature." "It is definitely about a brief experience that I had in my [life] - a long, long time ago," Duff, 38, told Vogue in a Thursday, November 6, interview. "It is not totally autobiographical. I took a few artistic liberties just to make the song work structurally, but the gist is the gist." She continued, "I was looking back on this relationship and thinking about whether this guy had a habit of dating younger women or whether I was 'special.