The girl-on-girl contact planted a seed of doubt in Alderman's mind about why such otherwise ordinary, pleasant people were condemned within her community. "So I grew up realising that there were perfectly nice, reasonable people who were gay, which did cause me to think about the way that Orthodox Judaism relates to gay people and that, actually, I'm not so happy about this," Alderman tells me at her flat in the north London suburb of Hendon, where her debut novel, Disobedience, is set.
Among those who are equally unhappy are some members of North London's Orthodox community, shocked and embarrassed that one of their own has written a novel about a rabbi's daughter from Hendon who becomes a lesbian. Alderman, 31, laughs off the suggestion that the novel is about her own coming out. Rather, it is a fictional exploration of the boundaries within which many Orthodox Jews live and the dilemmas that the intrusion of contemporary society often poses for them.
Alderman's heroine Ronit fled Hendon for New York after her father discovered that she was having a sexual relationship with her school girlfriend, Esti. But now that the Rav has died, six years later, Ronit must return to London to pay her respects and when she arrives, the welcome is decidedly mixed.
Alderman's novel has suffered a similar fate. "Some people in my community have been quite negative about it," she says. "People I know more distantly are horrified, but people I care about are extremely supportive." Her father, the historian Geoffrey Alderman, who writes a column in the Jewish Chronicle, is among her fans, and while her mother praised the novel, she added: "Darling, it's not the sort of book I would have read if you hadn't written it, but I did enjoy it."
Although Ronit is unrepentant, Alderman accommodates contradictions and remains an observant Orthodox Jew who keeps a kosher kitchen, doesn't use her car, her phone, money or check her e-mails on Saturdays and attends synagogue. Asked if she would consider marrying a non-Jew she pauses, genuinely torn about the implications of inter-marriage. "There are elements of my religion that I chafe against," she says. "But I never had that adolescent rebellious thing in that rather uncomplicated way where you say, 'it's all rubbish'."
Alderman, however, is still troubled about her religion's attitudes towards women and she gives me an example. If a Jewish woman wants to divorce her husband, under Jewish law, she needs his consent, which is known as a get. They can undergo a civil divorce, but without the get, the wife remains in limbo, unable to marry anyone else, while her former husband has the right to remarry since a man can have more than one wife under Jewish law.
Women like Alderman's character Ronit remain a problem in this closed community if they long for the power and authority that would be theirs by right if they were sons rather than daughters. "Ronit would have done better as a man and that's part of her problem and the community's problem," says Alderman. "There's nowhere to put very bright girls who don't immediately want to get married. I'm not so sure that's true of the intellectual orthodoxy that was my background, but among the Orthodox community of the Golders Green end ..."
The sentence is left unfinished as Alderman breaks off into a riff, her hands sailing through the air as she explains the differences between the Orthodox communities of Golders Green (conservative), Hendon (liberal) and Finchley (trendy/ vegetarian). But if she grew up wearing long skirts and using two sets of cutlery ("meaty" and "milky"), nothing stopped her ambition or intellectual development. From secondary school she won a place at Lincoln College, Oxford, to read politics, philosophy and economics.
From there Alderman was launched into the world, landing a job at an international law firm Freshfields Bruckhaus Deringer, editing their publications. After three years in London she persuaded the firm to send her to New York, where she shared an apartment with three other Orthodox Jewish girls. Unlike the bunker mentality of Hendon, she found the experience of her young Jewish colleagues, who maintained their religious practice but also had a wild time, very liberating.
"I met a lot of people in New York who were leading orthodox lives at the weekend but not during the week, and leading very modern lives, which was quite an eye-opener for me." But after six years of editing legal texts and working in the marketing department, Alderman headed home to Hendon and submitted an application to the respected creative writing programme at the University of East Anglia. Surprisingly, while the novel hasn't yet prompted anyone within her community to out themselves about their sexual identity, Alderman has encountered several closet Jews. "When I was at East Anglia I had three people in my tutor group who took me aside and said, 'I really enjoyed your novel because - and I don't talk about it much - but I'm Jewish,'" Alderman tells me. "There was one person I know who had been teased at school about being Jewish and went home to ask her mother, 'are we Jewish?' and the mother said, 'no, definitely not'." But the daughter later discovered documents that confirmed that her family were indeed Jewish.
THIS THORNY PROBLEM OF IDENTITY AND ITS rejection haunts Alderman's writing. Ronit finally decides that the world will just have to live with the fact that she is both Jewish and gay. Neither is a choice, but something you are born into. Alderman wonders whether there were British Jews, especially those who came with the Kindertransport during the Second World War, who lost their religion because of its painful associations. "It's a post-Holocaust thing," she says. "I think they are a bit of a lost generation and their grandchildren are now asking, 'what does being Jewish mean?' "
But while Alderman was careful to avoid references to the Holocaust in her first novel ("I thought it would just take over if I did"), she doesn't want to be pigeon-holed as an Orthodox Jewish writer. Her next novel is set at an Oxford college and involves a murder. "It's a cross between Brideshead Revisited and The Secret History," she says, grinning. "It does have a Jewish character, but not a Jewish theme." Alderman defies categorisation herself, revealing with giggling delight that not only is she a huge fan of Buffy the Vampire Slayer (a collection of videos line her bookshelves), she is a Buffy academic who has presented a paper on "madness and its parallels with Greek tragedy" to a Buffy conference in Nashville, Tennessee. "I feel very strongly about my TV," she adds. "One of these days I'm going to write a television series - I just know it."
When Alderman's not working on her second novel, she spends her time writing a story for a computer game called Perplex City, a map of which dominates her living room wall. "I have other strings to my bow," she says. "I hope that I get the chance to exercise those muscles. I have a deeply held belief that it's important to pursue anything that you're passionate about and part of that belief is to pursue without judgment. I love Buffy, I really do love it."
Alderman beams at me when I admit to being a Buffy fan, having watched it avidly with my daughters and marvelling that mainstream television has produced such a powerful heroine. Alderman gives me a meaningful look. "I'm glad you understand the importance of Buffy," she says. "She's a long way from Charlie's Angels."
And a long way from Hendon, too.
Disobedience by Naomi Alderman is published by Viking (12.99). The author will speak at Eastwood House, Giffnock, tomorrow afternoon as part of Jewish Book Week. Tel 0141-577 8210.