She's not the only one who thinks so; the press has in the past described her as everything from a "tantrum-throwing narcissist" to "a parody of celebrity". But it's hardly surprising she went off the rails: fame hit her from the wrong side of the tracks. During its nine-year run, her blue-collar sitcom, Roseanne, catapulted her from trailer-park to most recognisable comedienne on the planet.
The show, which reflected her humble origins, picked up four Emmy awards, and, at one point the star was taking home a reported £11.9m per annum. Barr would be the first to admit that she floated off into la-la land while living in the Hollywood bubble. She says the fact that she never washed her own underwear in those days is symptomatic of how divorced from reality she had become.
"I was in a sound studio for 10 years," she sighs. "For a decade, I wasn't in this world. At the end of it, like Rip van Winkle, I came back and found that everything had changed. Suddenly there were computers and e-mails, and it took me another 10 years to catch up with regular people. But the TV show is over. What am I going to do? I can't boss people around any more - sad but true. There is no one to frigging fight with any more."
She believes she has emerged from her struggles a better person. "I've been through a lot," she says, "but now I've come through to the other side. I've learned from my mistakes.
"What made me wake up and realise I was nuts? A lot of it is merely the process of getting older; you do get a little wiser as you go. For me, it's been 14 years of wising up - a gradual decision to fix what was wrong with me. Despite being a miserable old bat sometimes, I'm generally pretty happy with myself. I can look myself in the eye. Now I would not be embarrassed for God to be taping every scene from my life and showing it to the world. I'm feeling in touch with the good part of myself."
The good part of herself includes the domesticated mom who lives with her 10-year-old son, Buck, in El Segundo, California, but she retains her jagged edge. She has taken out an ad in The Hollywood Reporter saying: "this town is a back-stabbing, scum-sucking, small-minded town, but thanks for the money." Equally, she is able to laugh about her own background: "I used to want to be a movie-star so I wouldn't have to live in trailers. Now that I make movies, I spend my life in trailers!"
Above all, Barr exhibits a characteristic which always plays well with British audiences: an ability to send herself up. When I suggest, for example, that she is manifesting a great deal of passion about her work these days, she deadpans: "That's just the drugs. They're clearly working."
Later, when asked if she still has unfulfilled ambitions, she replies, quick as a flash: "Yeah, porn." And then, when pressed on why Roseanne still plays for at least six hours a day on US cable channels, she muses that "it could be because the viewers think I'm so hot!"
She has not had any cosmetic procedures for 14 years . "That was my youth," she laughs. "Everybody's got to do some crazy stuff when they're young. Now I realise that everyone has to get old and die, but it was still a very bad experience. Everything has to have a consequence. So after my surgery, my nose dripped constantly. At the end of it, you look like an idiot. No one looks better after cosmetic surgery. Just pink and shiny.
"It's weird how your face looks after it's been plastic-surgery-ised - remember those grotesque scenes in Brazil? You can't smile so much and your eyes don't blink. They even sewed one of my ears back on crooked. Plastic surgeons are just out to make money. But people are addicted to that bullshit - unfortunately, they're not going to give it up any time soon."
Now sporting an attractive blonde mane and a much trimmer figure than in her sitcom heyday, Barr continues by railing against the slimming business. "If everything blows up in the wake of 9/11, the one bright spot will be the fact that the diet industry will be going up in flames along with everything else. Then people are going to be extremely thin real quick! I'm so excited about that! It's a billion-dollar industry that just uses fat people as lab-rats. There is nothing a fat person won't do if you tell them some product will make them lose weight - nothing apart from getting up off their fat asses and stopping eating like hogs!"
Brought up as a Jew in a working-class district of the strictly Mormon town of Salt Lake City, Utah, Barr dropped out of high school at the age of 17. Soon after, she was involved in a serious accident which left her with memory loss and terrible nightmares.
She spent a year in a state psychiatric hospital before having her first child, Brandi, whom she had to give up for adoption. She then took a job as a dishwasher and waitress in a Denver restaurant. There, her larger-than-life personality meant that she was soon performing stand-up to her customers rather than serving them hash browns and grits.
She was spotted by Johnny Carson's Tonight Show and made her debut on that influential programme on 23 August, 1985. That night, Carson, then a great star-maker, predicted that Barr would become "the biggest woman comic ever". He was right. She launched her global-hit sitcom, Roseanne, three years later. But pretty quickly, things began to spiral out of control for the comedienne. Public vitriol rained down on her after she spat and clutched her crotch during a deliberately out-of-tune performance of "The Star-Spangled Banner" at a baseball game in San Diego.
Then she claimed that she and her siblings had suffered sexual abuse at the hands of her parents. The parents and the siblings denied the charges - her mother and father took lie-detector tests to prove their innocence - and Barr later withdrew them. However she did not speak to her parents or her siblings for a decade.
In 1990, she left Bill Pentland, her husband of 16 years and the father of three of her children, Jessica, Jennifer and Jacob, for Tom Arnold. Within four years, though, she had split from Arnold, accusing him of domestic violence. She married her bodyguard, Benjamin Thomas, in 1995.
She reversed a tubal-ligation procedure to have a son, Buck, with Thomas. But just three years later, she had filed for divorce against him, alleging that he was a binge-drinker who had threatened to abduct their son. Roseanne was axed, in 1997, after nine years and 224 episodes.
Now, after almost a decade out of the limelight - a talk show, a reality show and a cookery programme all failed - she has gone back to her Denver-restaurant roots and relaunched herself as a stand-up comedian. The show - which bears the telling title Let the Healing Begin - has been a sell-out in the States. This week, Barr is making her stand-up debut over here.
Barr re-acquired the taste for live performance in 2004 when Michael Moore invited her to come and win over the crowd in her home town of Salt Lake City. "It's a very right-wing place and they were throwing a fit about Michael coming there," Barr recalls. "So I thought, 'why not?' It was a tough crowd - a lot of them had come there to boo Michael. But as soon as I got going, it was the most fantastic fun.
"The atmosphere was very, very charged because it was just before the presidential election. So I went on stage and pretended to be a Bush supporter. I said, 'I'm glad he's President,' and they stared at me, like, 'what?' And then I continued, 'and I'm glad he vetoed the ban on assault weapons because you never know when God is going to call on you to shoot an abortion doctor.' It took about a minute for the audience to get what I was doing."
Barr has met Bush - and was not impressed. "I went up to him at a party, looked him right in the eye and said, 'Mr President, I pray for you every single day.' And you know how he replied? 'Aren't you a good girl?' Good girl! I was 50 at the time, for God's sake! Now I pray for him extra hard - that he will use the brain that God gave him."
Roseanne Barr stars in 'Blonde and Bitchin' at the Leicester Comedy Festival (0116-233 3111; www.comedy-festival.co.uk), tomorrow and SaturdayReuse content