Nicole Richie has some thoughts about Hilary Duff's new track - which is rumored to be about the reality star's hubby! Last Friday, the singer made a return to music for the first time in a decade. She is back with a new single called Mature, and it looks back on a past relationship with an older guy who used to say she was mature for her age. The lyrics read: "She looks like she could be your daughter / Like me before I got smarter / When I was flattered to hear you say / You're so mature for your age.