Brittany Murphy's last known photo, shot at a fashion event on December 3, 2009 in Los Angeles.

Brittany Murphy worked hard to be happy, was constantly looking for love and approval, and struggled to find work as she got older in Hollywood, a source close to the actress told Fox411.com.

“[Brittany] tried to make it seem like she was happy all the time,” the insider said of Murphy, who died on Sunday of an apparent heart attack at the age of 32. “She sought out love and affection and  wanted to find true love with [husband] Simon [Monjack] after a slew of messy relationships.”

Murphy had been engaged at least twice, to actor Ashton Kutcher and production assistant Joe Macaluso.

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The insider said Murphy had her share of personal problems, too.

“Brittany was not the healthiest person, and had Hollywood demons,” said the insider. “She was very hard on herself. She wanted more work, bigger roles, and married Simon quickly because she wanted the comfort she thought a husband could give her.”

Murphy and Monjack married in a private ceremony in 2007, just months after she broke up with fiance Macaluso. The source said the actress, “felt happiest when she had a man in her life and she was working. Brittany equated her success to love and work.”

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But the friend said Brittany had trouble landing roles as she go older.

“She had so much success as a child actor, and she worked her butt off at auditions to land new roles,” said the source. Murphy shot to fame as a teenager after starring in the hit 1995 film “Clueless.”

The job that kept her going? Her voice-over role on ‘King of the Hill.’

“She loved ‘King of the Hill’” the source said. “Doing the voiceover for Luanne was a great job that she was so grateful to have as she went out for other acting roles. ‘King of the Hill’ was steady work.”

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Brittany’s mother Sharon was in her home when her daughter apparently collapsed in the shower Sunday. The insider said Brittany’s mom has often lived with her over the years.

“Sharon was the one constant in her life,” said the source. “She dearly loved her mother and wanted her with her at all times, even after she married Simon. Sharon lived with them, and that was normal.”

Former fiance Ashton Kutcher sent his love to her mother Sharon when he Tweeted his condolences on Sunday. Murphy’s father, who had spent time in prison, said he had not been in touch with his daughter for years.

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“Brittany worked so hard to like herself and to make sure people liked her,” the source said. “It was always a struggle, but she was loved. This was an unnecessary death.”