Duff's No Fan Of Her Ex's New Squeeze

Hilary Duff is apparently in disbelief that her ex is dating Nicole Richie, Us Weekly reports.

"She can't believe he's dating Nicole and thinks she's a skank," a source tells the magazine.

Duff and the Good Charlotte singer Joel Madden, who reportedly split in November, has been linked with the "The Simple Life" star for the past month. Richie was busted for DUI when she failed a sobriety test Dec. 11.

When Duff learned of the arrest, "she asked if Nicole had been coming from Joel's," the source said. "She kept saying she never knew Joel at all."

One day after Richie's arrest, she was greeted by a throng of paparazzi as she left Madden's home in Glendale, Calif., TMZ reported Dec. 12.

An Us Weekly source says Madden has been calling Duff, but she "doesn't want to talk to him."