Stephenie Meyer's subconscious has a lot to answer for. Almost 10 years ago, as a young mother in Arizona, she had a dream about an average teenage girl and a beautiful male vampire, sitting in a meadow, lost in conversation about the difficulties of their relationship. The specific problem was that if they became too close – if they gave in to the girl's intense desires – he'd hurt and potentially kill her. Meyer wanted to remember the story, but was struggling with her small sons' relentless needs, so began writing it down for safe keeping. It was the first story she had ever put to paper. A modest woman, a committed Mormon, she loved books, had always conjured up stories, but had previously thought the idea of writing anything herself would be presumptuous.

That story became Twilight, the first of four books in a saga that has sold more than 100m copies, been translated into 37 languages, spawned a bogglingly successful film franchise, a much-discussed relationship between the film's young stars Kristen Stewart and Robert Pattinson, and a flood of visitors to the small town of Forks, Washington, where the series is set. In 2008 the novels occupied the top four places on the USA Today roundup of the year's bestsellers. In 2009, they repeated that trick. They have also inspired another colossally successful series; EL James has said her Fifty Shades of Grey trilogy, about a young woman who falls for a sexual sadist, began as Twilight fan fiction. When I ask Meyer whether she's read Fifty Shades, she quickly, emphatically, says no. She doesn't wish James ill at all, she says, but "it's so not my genre. Erotica is not something I read. I don't even read traditional romance." Why not? "It's too smutty. There's a reason my books have a lot of innocence. That's the sort of world I live in."

Beyond her outstanding contribution to the survival of publishing, the most interesting outcome of Meyer's work has been the window it has opened on the desires of a generation of girls. Just what is it about the controlling, mercurial vampire Edward Cullen – a character who constantly tells his girlfriend he's dangerous, who constantly polices the couple's sexual boundaries – that they're so drawn to? Meyer's public appearances often inspire febrile crying from fans, the shaking and sobbing more usually associated with devoted Beliebers. The day we meet, she is due at a book signing in the evening, and reports have arrived that girls are already camping out, wrapped up in silver survival blankets.

The film she is promoting, The Host, is based on a book she published in 2008, which also topped the bestseller lists. I can't describe the film, since the publicists weren't too keen for me to see it; suffice to say it has an interesting cast including Saoirse Ronan and William Hurt, and an interesting director, too, in Andrew Niccol, who directed and wrote Gattaca and also wrote The Truman Show. Meyer's novel is a science-fiction story about a world in which aliens have taken over the Earth, very few humans survive, and those who do run the risk of having their body co-opted, an alien soul implanted in their neck.

Meyer, who is now 39, wrote the book because she needed an "escape from my original escape", she says. Since she published Twilight in 2005, her life had become surprisingly stressful. She had anticipated an indifferent response to the novels – she is remarkably unassuming – but instead there came "the massive amount of fans that I hadn't expected, and the massive amount of people who hated it, which I also didn't expect". Twilight's critics have certainly been excoriating. The books have been accused of being "abstinence porn", a series deviously designed to convince teenagers of the need for sexual purity, centred on one of the blankest female characters ever created in Bella Swan, a girl defined by low self-esteem, who has few interests besides worshipping her vampire boyfriend. It has been suggested that they eroticise domestic violence, and push an anti-abortion message, and there has been brutal criticism of their literary merits. (Stephen King famously said Meyer "can't write a darn. She's not very good.") Not surprisingly, she found some of the responses tough to take.

Today she seems relaxed. Meyer is now also a film producer, a role that began with the final instalments in the Twilight saga, and includes an upcoming adaptation of her friend Shannon Hale's novel Austenland, about a Pride and Prejudice fan who goes in search of her own Mr Darcy. She also produced The Host, and says it was important for her to portray a positive relationship between the two women at the centre of the story: Melanie, a resistance fighter, and Wanda, the alien implanted in her neck. (If ever you need to have a good relationship, I suppose, it's when you're forced to share the same body.)

Max Irons and Saoirse Ronan in The Host. Photograph: imagenet

Despite all the criticism of her work, Meyer says she is a feminist, and that this is really important to her. "I think there are many feminists who would say that I am not a feminist. But, to me ... I love women, I have a lot of girlfriends, I admire them, they make so much more sense to me than men, and I feel like the world is a better place when women are in charge. So that kind of by default makes me a feminist. I love working in a female world." She was thrilled when Catherine Hardwicke's adaptation of Twilight made her one of the most commercially successful directors in Hollywood, and says of working on Austenland: "It was almost an entirely female production, which is so rare, and to be able to work with female writers and female directors and even our co-producer was a woman – it was a totally different feel than you would have on a more traditional, male-centric set."

The Host was also inspired by her feelings about body image. Meyer is attractive – when she speaks, she resembles the actor Julianna Margulies – but she doesn't seem to see it. "As I was writing The Host, one of the things that made it really interesting was the idea of looking at being human from the perspective of someone who hasn't been human their whole life," she says, referring to the Wanda character. "You know, you usually wake up in the morning and think: 'Ugh, I look horrible, I hate myself, I don't want to walk out the door like this.' And it's nice sometimes just to stop and think, I can walk out the door and see everything outside of it, and that's amazing."

Meyer was brought up in Phoenix, Arizona, by a mother, Candy, who stayed at home to look after the six children, and a father, Stephen, who worked as a financial officer. (She was named after him, hence the quirky spelling of Stephenie.) She was the second child, and soon became "the book girl. I spent my entire childhood reading, and I think I was a bit annoying because I was always living in a fantasy world." On going to the Mormon university, Brigham Young, to study English, her modesty and respect for great writers stopped her attending creative writing classes. "When I was growing up, authors were amazing angel people who had gifted me these other worlds I got to live in, and I would never put myself on that level," she says. "You know, I was an English student, and there were people there who said they wanted to be writers, and I completely scoffed. Like, first of all, you can't make a living doing that. Secondly, who are you to presume you can write novels?"

While still at university, aged 21, Meyer married her husband, Christian, an accountant; they had met at church when she was four, and started dating nine months before their wedding. The family is religious, she doesn't drink or smoke, and she is glad the profile of Mormonism has risen a little recently, so there aren't so many embarrassing questions or misguided stereotypes. For instance, the first time she went to meet her agent, "we were on a train, and she said: [her voice drops to a whisper] 'So, how many wives can you husband have?' And I was like, 'Well, just one, if he wants to keep the one he already has.'"

She worked briefly as a receptionist, then had her three sons, Gabe, Seth and Eli. For all that they're wonderful boys, she says, their early years were one of the roughest patches of her life. "They didn't sleep, they all had colic and ear infections endlessly, and so I just didn't sleep for six years. I was always tired, and I always had a crying baby on me somewhere. My whole life was about basic survival. About keeping them breathing and fed."

Then came the vampire dream, and the compulsion to record it. She finished the novel in three months, her older sister encouraged her to send it out, an agent snapped it up, and within a few weeks she had a book deal from Little, Brown worth $750,000 (about £500,000). She knew the book was successful when it reached the New York Times bestseller list; she knew the series was a phenomenon when the first film was in production and fans bombarded the film-makers with emails, and kept sneaking on to the set.

The criticism also kicked in, growing stronger with each book. In person, Meyer's demeanour makes you want to defend her; while what she says often sounds prim on the page, she's actually a lot of fun, direct and friendly, with a winning line in bigging up those she works with, especially women who aren't necessarily at the top of the tree. Unfortunately, the books are tough to defend. There's no doubt, for instance, that Bella is a remarkably droopy, drippy character, and while her blankness could be justified as a device, enabling readers to identify with her (which has obviously happened to an extraordinary degree), she also has a weird clumsiness, a haplessness that means her vampire boyfriend has to rescue her regularly. He warns her constantly that he could hurt her, while his moods swing wildly. These traits only thrill her more. The oddness of their romance led some readers to point out that it exhibits many of the classic signs of an abusive relationship.

Meyer's editor asked her to include pre-marital sex scenes, but she declined. Did she set out to promote an abstinence message? "You know, it's so funny," she says. "I never decide to put a message in anything. I decide on a story that I think is exciting, and I entertain myself, and then some of it obviously reflects my personal experience … What I think says true love is different than what a lot of other people do, so it's just what my subconscious puts out there. To me, true love is that you would hurt yourself before you would hurt your partner, you would do anything to make them happy, even at your own expense, there's nothing selfish about true love. It's not about what you want. It's about what makes them happy."

Taylor Lautner, Kristen Stewart, Stephenie Meyer and Robert Pattinson at The Twilight Saga: Breaking Dawn - Part 2 premiere in LA. Photograph: Jeff Vespa/WireImage

Ironically, the criticism only intensified when the couple finally had sex in the last book, Breaking Dawn, after getting married. The scene takes place off the page, and the next morning, Bella looks at herself naked in the mirror: "There was a faint shadow across one of my cheekbones, and my lips were a little swollen, but other than that, my face was fine. The rest of me was decorated with patches of blue and purple. I concentrated on the bruises that would be the hardest to hide – my arms and my shoulders." Despite these injuries, she is desperate to have sex again. When their relationship leads to a pregnancy that looks likely to kill her, she refuses an abortion, only to have her bones snap during the birth.

Was Meyer worried about how Bella's post-coital injuries might be seen? "To me, it was this really obvious situation," she says. "He is 100 times stronger than her. He's been telling her, for three books, that this is a bad idea. It would have felt really false to me if: 'Oh, whoops, there was no problem at all!'" I ask whether she's anti-abortion, and she says: "You know what? I never talk about politics, because that is one of my pet peeves, when people with any measure of celebrity get on their soapbox and say: 'You should vote this way.' First of all, celebrities don't know anything about real life. They live in an ivory tower … I lived in the real world for 30 years, enough to know I'm not in it now."

She says the way Bella responded to her pregnancy related to her experience of carrying her first child, Gabe. "I was told that I was having a miscarriage, and that was one of the darkest times of my life. And so, for me, I knew I could relate to her. Bella had been OK with the idea of being childless, but [when the character became pregnant] I was back in that time of my life when someone told me that that was going to be taken away from me … That was something I'd been through that really affected my life, and it was not a commentary on anything political." Thankfully, her son was fine, "but I have had friends who have lost children, and I know the hole that creates when you really want that child."

The truth is there must be tens of thousands of romance novels containing similar themes and biases to Meyer's series: weak heroines, strong heroes, submission and surrender, a central plot involving obsessive love. Had the Twilight books sold 5,000 copies, it's doubtful anyone would have complained. The most interesting question is not why she wrote it as she did, but why girls responded so wildly. Is there something particularly powerful, in this cultural moment, about a dangerous, potentially violent romantic hero? In a world where porn is ubiquitous, where there do seem new sexual pressures on young women – demands for them from boys to take naked pictures, for example – is a chaste but adoring partner especially appealing? Do young women still yearn for a dominant man? Do they identify, more than ever, with an awkward, unconfident female protagonist? Bubbling away in a generation's subconscious are some troubling answers.

The Host film tie-in book is published by Sphere, priced £7.99. To order a copy for £6.39 with free UK p&p, call 0330 333 6846 or visit guardianbookshop.co.uk. The film of The Host is released on 29 March