Time was when child stars like Hayley Mills and Jenny Agutter grew up under the excruciating gaze of a doting public. Signs of physical maturity and boyfriends were reported in tones of reverent incredulity. Watching the metamorphosis of the singer Charlotte Church, by contrast, evokes the alarming extra-terrestrial shape changing of the film Alien.

Only yesterday, it seems, Church was an angelic-looking Cardiff soprano with a golden voice, plaits and a schoolgirl smile, singing against a background of rolling Welsh hills. Little girls idolised her and women wanted to mother her.

Suddenly she was in our faces as a curvaceous, foul-mouthed hellcat who smoked, rowed with her mother, got “bladdered”, dated a succession of unsuitable boyfriends with a penchant for selling their stories to the tabloids, and slagged off her peers. Her growing pains were everyone’s, whether they wanted them or not.

Last week the 19-year-old millionairess underwent a further transformation to something approaching the butterfly stage. The drunken milkmaid of recent memory morphed into a poised and svelte temptress for a men’s magazine photoshoot, signifying a musical change of direction from classical music to pop.

Wearing a revealing basque top, black stockings and wig of Roxie Hart from the musical Chicago, Church was unrecognisable. So is her singing on her new album, Tissues and Issues, in which she harnesses her extraordinary voice to the buzzing pop songs of Motown and a thumping house beat.

It looks like the final nail in a brilliant operatic career that led her to perform for the Pope, the Queen and two American presidents. (She found George W Bush “very pleasant”, and Bill Clinton “had that charisma”.) Her search for a new audience is bearing fruit: Crazy Chick, a single from the album, entered the charts at No 2.

Church’s new image slipped slightly when she characterised 2Pac’s No 1 record, Ghetto Gospel, which features Elton John, as “crap”. Perversely her blunt candour is cherished by tabloid commentators who credit her with rejecting the industry’s insipid culture of sugar and spice.

Last week she was hailed as a breath of fresh air after her bitchy attack on Rebecca Loos, who claimed to have had an affair with David Beckham: “She needs to get a job, put her tits away because they’re horrible, and get a nose job.”

Not surprisingly she has won a ringing endorsement from another singer of outspoken views, Liam Gallagher of Oasis: “She knows how to get f****** hammered and she freaks people out.”

Her extempore remarks have not always gone down well. Despite calling out “I love America” to a roomful of Canadians, she appeared to criticise New York’s firefighters who lost dozens of colleagues on September 11, saying: “They went from here in society to celebrities. They are even invited here to present television awards, which I don’t agree with.” She was voted 21st “worst Briton” in 2003.

Her excesses notwithstanding, it is apparently impossible to dislike her. She owes her newfound status as “the nation’s sweetheart” in part to behaving like any other 19-year-old. Resisting the lure of London she has stayed in Cardiff to be near her family and friends and pays herself only £300 a week from a fortune reported to be worth £6.5m-£16m from her huge record sales.

Her popularity has been enhanced by her romance with Gavin Henson, the British Lions rugby star who helped Wales to win the grand slam at the Cardiff Millennium stadium, where Church sang the national anthem before the game.

There is even talk of the couple becoming the next Posh and Becks — an idea she dismissed as “bollocks”, adding tartly: “I can sing!” Unfortunately, several critics have noted that her latest album is just the sort of thing the Spice Girls might have produced — a homogenised concoction of anodyne music and cliched lyrics that does not do justice to the most gifted singer of her generation.