"Clueless" director Amy Heckerling echoed Bertolotti's comments in an interview for a Los Angeles Times blog on Sunday.
"Everybody's shaking their heads and going 'drugs,' of course. I don't know what was happening on the last movie. I know that, you know, she seemed to go through a change ... on 'Clueless,'" Heckerling said.
"Maybe she felt like she was not the, like, skinny, pretty girl, you know? And then the next few movies she was, you know, thinner, blonde ... and going out with Eminem and Ashton Kutcher, and, you know, suddenly got more into that whole glamorous scene," she said. "I think she felt the pressure to become a different sort of commodity to survive in show business, and I think it was awful."
One of Murphy's friends told People magazine many of her problems were due to poor self esteem.
"She wore extraordinary amounts of makeup, tons of fake eyelashes, got her teeth capped, dyed her hair blonde, lost weight -- she wanted to be a beauty," the friend said. "She didn't want to be the fat girl from 'Clueless.' She didn't eat a lot. She would drink copious amounts of coffee."
Recently, reports had emerged that Murphy was behaving erratically on movie sets and had been fired from her last film, "The Caller," which her rep denied.
In her final red carpet appearance on Dec. 3, Murphy appeared gaunt.
"We noticed here last week how incredibly thin and unhealthy she looked," US Weekly senior editor Bradley Jacobs told ABCNews.com. "She appeared skinnier than ever."
She may not have looked well when she attended the boutique opening in Los Angeles, but Murphy was excited about the future.
"As far as having a New Year's resolution, I'd love to have a child next year," she told "Access Hollywood." "But that's kind of a large one."
When she first revealed a radically slimmed-down figure in 2002's "Spun," the tabloids linked her weight loss to cocaine. Three years later, she tried to set the record straight.
"I have never tried it in my entire life," she told Jane magazine. "I've never even seen it. ... It couldn't be further from the truth."
Before that, in 2001, she told a columnist for the entertainment blog TheWrap.com that she would never take drugs because she had a heart condition.
"It was in an interview about 'Sidewalks of New York' but I asked her about other projects and she mentioned 'Spun,'" columnist Michael Adams recalled for the Web site. "I asked her -- as a joke -- if she'd taken meth for research and she laughed and said even if she wanted to she couldn't take drugs because she'd had a heart condition since she was a little girl."
Murphy also denied having an eating disorder.
"I'm the same size I was in 'Clueless;' it's just that the weight in your face changes as you grow and get older," she said in 2005 while promoting "Sin City." "This is my body. I'm proud of it. ... I'm healthy."
But others questioned just how healthy she was.
"A lot of people weren't surprised to hear about [the death of] someone who for years was rumored to have problems with substance abuse," E! gossip columnist Marc Malkin told ABCNews.com. "You saw the photos of her looking painfully thin? In this industry where there's smoke, there's fire. When I heard it, I was sad but not 100 percent surprised."