She was the Seventies folk icon, endearingly gangly and blonde, who sang sweet, heartfelt ballads as she strummed an acoustic guitar.

But then she became music's bitter Greta Garbo, emerging from her reclusive life to lob verbal hand grenades at all manner of people - singers Bob Dylan and Taylor Swift, hippies and feminists.

Joni Mitchell, widely acclaimed as the greatest female singer-songwriter in pop history, creator of such hits as Big Yellow Taxi, Woodstock and Both Sides Now, has always been an enigma.

But the biggest mystery about her emerged last week with the revelation that a longtime friend had filed legal papers to become her guardian.

At a brief hearing on Monday, a Los Angeles judge agreed to put the friend, fellow music industry veteran Leslie Morris, in charge of the care and daily affairs of the multi-millionaire music legend.

The world already knew that Mitchell, 71, had been taken to a hospital in LA on March 31 after being found unconscious on the floor of her home.

But then the confusion started. Without going into detail about what had happened, her official website soon carried a statement implying all was well: Mitchell had regained consciousness and, though undergoing tests in intensive care, was 'awake and in good spirits'.

The site urged fans to 'light a candle and sing a song, let's all send good wishes her way'.

Then came the news that would have snuffed out every candle lit by Mitchell fans. The legal petition filed by Miss Morris, who said she and Mitchell had been friends for more than 44 years, attested that the singer 'remains unconscious and unable to make any responses, and is therefore unable to provide for any of her personal needs'.

The singer's doctor, Paul Vespa, a professor of neurology and neurosurgery, agreed.

He said Mitchell's mental faculties - including being able to communicate, recognise objects and people, and to have any sense of her surroundings - were so impaired as to be incapable of being assessed. She was unable to give her consent to medical treatment.

The word 'coma' wasn't mentioned, but the expert medical assessment certainly suggested that the singer's condition was not far removed from it.

Horrified, celebrity fans poured out their feelings on Twitter. Actress Emma Watson, the 25-year-old star of the Harry Potter films, confided that she 'hadn't been able to concentrate all morning' since hearing the news - proof that Mitchell's bewitching appeal had endured down the generations.

Still, Dr Vespa hadn't give up hope. He noted that he expected the singer's condition to improve sufficiently for her to attend a court hearing in four to six months.

The official fans' website also sounded robust. In a statement released on April 28 - significantly, just hours after the court petition was posted online - an even rosier picture was suggested.

'Joni is not in a coma. Joni is still in the hospital - but she comprehends, she's alert and she has her full senses,' it said. 'A full recovery is expected.'

A recovery that will, however, be closely directed and supervised by Miss Morris.

When the petition was heard on Monday, her lawyer told Superior Court Judge David Cunningham that Mitchell 'could be leaving hospital soon', citing her impending discharge as one of the reasons why Morris should be granted emergency powers as a 'conservator' - a role that under U.S. law gives the holder power over someone's affairs and day-to-day life, although not in this case their finances.

The official website stressed how the role adopted by Miss Morris 'simply gives her longtime friend . . . the authority - in the absence of 24-hour doctor care - to make care decisions for Joni once she leaves the hospital. As we all know, Joni is a strong-willed woman and is nowhere near giving up the fight.'

By yesterday, more than 13,000 Mitchell fans, wondering whether they would ever hear her sing again, and why Mitchell could not make her own care decisions, had posted messages of support for the star on a tribute website, weloveyoujoni.com.

Beyond hoping that their idol would soon leave hospital, there was little further encouragement to be had from Monday's court hearing as no more details of Mitchell's condition, or of her prognosis, were disclosed.

The contradictory reports, and a wall of silence to media inquiries, have left them still fearful for her health, wondering whom to believe: doctor, or publicist?

Though her name may be unfamiliar to Mitchell fans, Leslie Morris is the former manager of the 1970s band Crosby, Stills, Nash & Young, one of whose members - Graham Nash - was one of Mitchell's lovers back then.

Morris is also the widow of Hollywood documentary-maker L.A. Johnson, who made a film about Mitchell 35 years ago, called Shadows And Light.

If the document filed by Miss Morris paints an uncertain picture of Joni Mitchell's future, it also hints at the tormented private life of the gravelly-voiced singer, who in her glory years had flings with the Hollywood lothario Warren Beatty and the musician James Taylor, partied with The Beatles and the Rolling Stones and saw her albums, with their confiding, confessional lyrics, go platinum.

Mitchell's latest medical crisis is just one in a long line of threats to her health. An only child, she was just nine years old when she contracted polio. She defied doctors' predictions that she would never walk again, recovering after treatment in a children's hospital, where she sang at the top of her lungs, despite having already started smoking cigarettes - which became a lifelong addiction.

Although she has complained of poor health for decades, it wasn't until 2010 that Mitchell first said she was suffering from Morgellons, a rare condition widely thought by doctors to be delusional, in which victims believe they are infested with disease-causing fibres and parasites. It was identified only in 2002 by a Pennsylvanian lab technician.

'I have this weird, incurable disease that sounds like it's from outer space,' the singer declared.

'Fibres in a variety of colours protrude out of my skin like mushrooms after a rainstorm ... they cannot be forensically identified as animal, vegetable or mineral.

'Morgellons is a slow, unpredictable killer - a terrorist disease: it will blow up one of your organs, leaving you in bed for a year.'

Like many of the other estimated 1,400 sufferers in the U.S., Mitchell is convinced that parasites are living under her skin - a condition that scientists call 'delusional parasitosis'.

At times, she said, she couldn't wear clothing as she continually felt that she was being 'eaten alive', and was unable to leave her house for several years. Sometimes, she felt her legs cramping up so much that she could not walk, and had to crawl across the floor instead.

While Morgellons is often described politely as a 'mysterious' disease, the overwhelming medical opinion is that sufferers have a psychological - rather than a physical - illness.

Many victims appear to have had a history of drug-taking. Predictably, given her counter-culture past, Joni Mitchell has admitted to taking a lot of drugs over the years.

She says she was addicted to cocaine in the Seventies. When she went on a concert tour headed by Bob Dylan, and was asked how she wanted to be paid, she replied: 'In cocaine.'

While she accepts that smoking has ruined her voice, and says she also suffers from acute insomnia and paranoia, Mitchell blames Morgellons for deterring her from performing, recording, or even travelling in recent years.

As one sympathetic doctor put it this week: 'Imagine you're at Madison Square Garden, singing for thousands ... and then all of a sudden you feel the itch. Spiders have begun creeping across your limbs, rashes spread over your face and under your skin.'

Is it possible that Mitchell's latest spell in hospital may be the result of a psychiatric, rather than a strictly physical, condition?

That would certainly go some way to explaining the confusion about her condition, and also the apparent speed of her recovery.

Her friend Miss Morris, in her court submission, claimed that Mitchell had confided 'over the years' that she no longer had any living relatives who could care for her, hence her own offer to take on that role.

In fact, Mitchell does have a living relative: an illegitimate daughter she gave up for adoption as a teenager but who came to find her birth mother 30 years later.

Mitchell was 19 and at art school in Canada when she became pregnant by a fellow student and gave birth in 1965. Not until 1997 did her daughter, Kilauren Gibb, make contact.

By then, Gibb had two children herself, a boy and a girl, making Mitchell a grandmother.

Initially, the reunion was rapturous. They met in a blaze of publicity at Mitchell's $9 million mansion and Gibb said of their first hug: 'It felt like I'd gone away on a trip for a couple of months and I was coming home.'

However, the relationship soon soured. Mitchell blamed 'abandonment issues' and poor behaviour by Gibb, who had worked as a model after being brought up by a prosperous Canadian family.

In 2000, police were called to Mitchell's home when Gibb claimed her mother had attacked her. Amid growing tension, mother and daughter were once again estranged. It was a bitter blow for Mitchell, who then retreated from public view.

In recent years, she has emerged to brand her contemporary, Bob Dylan, a plagiarist and a fake, and to dismiss singer Taylor Swift - who was tipped to play her in a biopic - as just 'a girl with high cheekbones'.

It seems the singer has lost none of her innate feistiness, which she will certainly need in the coming weeks and months.

'I have a tremendous will to live,' Mitchell told a newspaper in 2010. Her fans will certainly hope that she comes through this latest battle with her fighting spirit intact.