According to Us Hilary Duff thinks Nicole Richie is a “skank.”

Nicole has been dating Hilary’s ex Joel Madden for the past month. He has been calling Duff, but she “doesn’t want to talk to him” (the pair split in late November after two and a half years). Adds the source, “She can’t believe he’s dating Nicole and thinks she’s a skank.”

When Duff, 19, heard about Richie’s arrest, “she asked if Nicole had been coming from Joel’s,” says the source. “She kept saying she never knew Joel at all.”