Long before Lily Allen rhymed weight loss with Kate Moss, before Martha Wainwright recorded a song about her dad called Bloody Mother F***ing Asshole, before Amy Winehouse sang about footballers' wives wearing f***-me pumps and Kate Nash commemorated the pimples on her face in song, there was another. A breakthrough woman in the tell-it-how-it-is school of songwriting.

If you came of age in the mid-1990s, Alanis Morissette was a revelation, barely out of her teens herself. She wasn't so much confessional as confrontational; tunefully shrieking out the contents of her Canadian heart with a rock-meets-power-pop appeal. Well, that's if you were a girl. If you were a boy, it's quite likely you thought she was a whiny, me-me-me type, wailing her way through long sentences of rambling, unhinged whinge. Either way, Morissette turned that self-assertion into catchy songs, and become a massive star - her Jagged Little Pill album alone sold more than 30 million copies worldwide. So imagine my horror to discover now that it was only in her songs that she was so forthright.

“You mean because in You Oughta Know I sang about going down on somebody in a movie theatre, was I the sort of person to just announce that in a room full of people? No, no way! There was no duplicity, because I was doing what I was writing about, so the lyrics are all accurate, but...” We are sitting in a London hotel, her speech calm and measured until the 33-year-old lets out a whoop, “But... especially in F***ING RELATIONSHIPS! I'd be really direct in a song and then I'd be with a boyfriend in the middle of a conflict and I'd be - ‘I just have to go to the other room and write a song and be right back!'” She was afraid of not being liked. Now, she quite honestly comes across as the least angsty person I have met.

Morissette was the child of teachers in Ottawa and has two brothers, one of whom, her twin, is now a yoga instructor. She began piano lessons aged 6, and later appeared on Star Search, an American talent competition, which she lost. By 14 she had a record deal and became the Debbie Gibson of Canada with two albums of teen pop, but after leaving school she moved to LA, got mugged and began having panic attacks - an episode that somehow led to her creative rebirth, and the records that would make her an international star.

“As a kid I was this overachiever who was taught that I would only be loved if I was perfect. So get A-pluses, look perfect, act perfect, smile when you're angry, don't cry. This impossible persona of - what? - something that isn't sustainable. So my challenge was to unravel, because I was wound pretty tight,” she says.

Carnal pursuits have helped, too. Having spent all her adult life as a serial monogamist, she decided to spend the last year doing things such as going to Fiji and “being quite debaucherous, really enjoying the sex, drugs and rock'n'roll lifestyle, finally! Ha ha.” She has written about this on her new album, Flavors of Entanglement, in the song Moratorium. “It's about the clarity, the exultation, finally bursting out of this self-imposed prison and just declaring that I would like to take a break because I was always the girl that would go from relationship to relationship and never have a breather. So taking a year off from any kind of commitment has been amazing. It's been such a rite of passage. Spending a year getting in trouble has been really, really fun.”

That's not to say she doesn't miss her former fiancé - the actor Ryan Reynolds, who split up with Morissette only last year and now appears to be engaged to Scarlett Johansson. How does it feel to see rumours of his engagement all over the papers?

At first, Morissette gives a Californian answer, talking about her own personal journey and wanting him only to be happy and blessing him for the role he played in her life, that she was not meant to marry him because she wasn't ready, she still isn't ready, she has a little growing up to do. We move on, but later she wants to revisit the question, “because I think it would be a lie for me to say that I didn't go through the depths of despair. But I'm a quick riser out of the ashes. If this was a week after [we broke up] - well, I wouldn't even have been doing interviews a week after. I couldn't even walk towards a fridge. It was rough then. At least I have some distance now.”

The album, which has some pretty rocking moments, begins with the sounds of sitar and tabla, on a song called Citizens of the Planet. Yep, Alanis is still on the spiritual trip that had begun when she sang “Thank you India” a decade ago. Her house near the sea in LA is run a little like a commune - old friends move in and stay as long as they need to. She rides motorbikes and hangs out down the Californian coast at Esalen, the New Age retreat once beloved of Kerouac and Anaïs Nin - she particularly enjoys the naked hot tubs. She is friends with the self-help author Byron Katie. She designs her own jewellery and has the word “gentle” tattooed on her arm. She met and sang for the Dalai Lama, “who was very sweet”, and sees auras around everybody.

She also, though you may not believe it, has a wicked sense of humour, revealed when Larry David cast her as herself in a send-up episode of Curb Your Enthusiasm. She also became a YouTube sensation with a most unlikely cover version of My Humps by the Black Eyed Peas, turning the throwaway chart hit about breasts, “my lady lumps”, into a comically painful Alanis aria.

“Fergie [Black Eyed Peas vocalist] sent me a cake in the shape of a butt and a note saying ‘You're a genius, Alanis!' She has a good sense of humour. Twelve million people have seen it now. I am in shock.”

One last question - has she worked out the meaning of irony yet? Because that song, Ironic, when she sang about rain on your wedding day and a traffic jam when you're already late, well, they weren't really the best examples of irony, were they? Her British audience were always a bit annoyed by that. “Oh not just the British - the whole planet! Yes, I've now learnt the definition of irony - but the dictionary now says that it's a coincidence and bad luck, too - not that I don't deserve a little slap on the wrist for my malapropism. I always tell people that I'm the smartest stupid person you'll ever meet,” she smiles. Nay, she glows.

The psychotherapist R.D.Laing, in later life, wrote about being much younger now than he had been when he wrote The Divided Self in his twenties. It's a bit like that with Morissette - now she's got through the serious business of being young, it's time for the fun to begin.

Flavors of Entanglement is out now on Maverick Records

Explore Music

• Proms

• Festivals

• CD Reviews

• Live Reviews

Editor's choice

• Are Glasvegas the new Oasis?
• 50 most memorable moments
• Vote for musical perfection