As Ashlee Simpson celebrated her husband Pete Wentz’s 29th birthday last week with a private bash in Hollywood, her sister Jessica Simpson was far from the spotlight, working hard to promote her new country album in Nashville.

Looking terrific in turquoise, Jessica cheerfully signed autographs for two hours at the CMA Music Festival in Nashville on June 6.

"She treated every individual with respect," a CMA staffer tells OK!, "and tried to talk to each person."

These days, the Texas native has good reason to turn on the Southern charm. The pop star turned actress, 27, is hoping to restart her career by returning to her roots and reinventing herself as a country singer.

"Back in the day, Jessica thought she was going to be the next Julia Roberts," a source close to the singer tells OK!. "The media attention went to her head and she became a different person."

No doubt! At the 2007 Costume Institute Gala at the Metropolitan Museum of Art in NYC, Jessica was virtually unrecognizable with dark hair, a darker spray tan and a skimpy Roberto Cavalli gown. She had a trendy boyfriend on her arm — John Mayer — and a group of hangers-on who traveled everywhere with her.

"Her entourage grew as her ego grew," says the source, "and then the bubble burst. She realized she lost herself, but now she is starting over."

Jessica’s second act, which includes her just-released single, "Come on Over," has been warmly welcomed by Nashville, mostly because she is working so hard to make her country career work.

"The country community is accepting of artists who are serious," GAC’s Country Music Across America host Storme Warren, who introduced Jessica at the CMA Music Festival Block Party on June 4, tells OK!. "Jessica has done it right."

Jessica herself has high hopes for the album. "I’ve been working on it for the past seven months now and I really feel at home with this music," she said at the CMA event.

Says a source, "The diva seems to have gone away and the real Jessica — the one with the big heart and goofy smile — is finally back."

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