Nicole Richie, Jessica Simpson Feuding on Fashion Star

Credit: Steve Granitz/; Dr. Billy Ingram/

Two blonde ex-reality stars turned fashionistas don't see eye-to-eye? Who could've predicted that one?

Nicole Richie and Jessica Simpson are both mentors on Fashion Star, a reality competition for aspiring designers debuting midseason on NBC. But a source tells the new Us Weekly -- on stands now -- that there's "definite friction" between the two women.

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"They chat only when they need to, and they have wildly different opinions about style," adds an insider.

Richie, 29, "thinks Jessica doesn't have much of a high-fashion eye" and "makes snarky comments about Jessica's outfits," according to a source.

But Simpson, 31, isn't phased by Richie's digs. She "really doesn't care what Nicole thinks," says an insider. After all, Simpson's fashion empire had $750 million in sales in 2010, while Richie's lines pulled in an estimated $10 million. 

"Nicole may know trends, but Jessica believes she know how to make clothes for all kinds of women," says a source. Still, other insiders tell Us the ladies "get along well, and hang out on set."

For more on Nicole and Jessica's Fashion Star feud, check out the new Us Weekly -- on stands now!