What's behind Nicole and Rachel's big bust-up

Call it a fashion divorce.

Nicole Richie and her longtime faithful fashion stylist Rachel Zoe have parted ways. And not all that amicably, according to TMZ, who printed Zoe's statement yesterday.

Most interesting is the phrase "being a good friend to Nicole." Wonder if that included advising Richie against getting breast implants, as many observers insist Richie has done.

"That's either the world's most amazing strapless push-bra or those are breast implants," said one reporter backstage watching the skinny starlet at the American Music Awards last week.

Perhaps Zoe, sweetly under-endowed herself, expressed disapproval of her fashionably coathanger-thin charge getting tacky Hollywood fake booblets.

"Nicole's not fooling anyone," said a Hollywood fashion insider. "She probably thinks that having bigger breasts will stop all the weight criticism. But it's so obvious that the only weight she's gained is silicone or saline. She's still got a serious problem."

At least Zoe doesn't have to hunt for frocks to show off these new puppies.

Photo Credits: Flat Nicole - before -  at Social Hollywood in June 2006.
Jeffrey Mayer/WireImage
Photo Credits: Full Nicole - after - backstage at the AMAs in Nov 2006. Hmmmm. Quite an increase in just five months.
Steve Granitz/WireImage