'Hi, this is me, I have scars to show you." The 20-year-old rapper Angel Haze begins talking casually about the most raw, unflinching song she has written but her words soon pour out, as though she has practised them in her head for years. "When I listened back, I felt disgusted. I wanted everyone to feel that. It was good that they felt it, because it was fucking wrong. I want someone who's a father to listen to the song, and be like: 'No one had better ever fucking touch my daughter like that. And if they do, you can tell me.'"

Quietly uploaded to her Soundcloud account last October, Cleaning Out My Closet – a version of the Eminem track of the same name – tackles the sexual abuse Haze endured between the ages of seven and 10. She spares the listener nothing: the graphic details of what happens to her body, the fury and trauma that run through her mind. Redemption comes at the end, but not before you're left physically reeling. "There are people who go through this shit every day, and people turn a blind eye," says Haze. "They're too scared to say what happened to them. To make people feel uncomfortable." Of all the responses she has had, the ones she treasures most are from fellow survivors. "Surprisingly, more boys than girls," she muses. "A lot of guys were like: 'I've been suffering, I don't know how to love anyone, you really helped me with that.'"

The brutal catharsis of Cleaning Out My Closet is in keeping with the no-holds-barred honesty that runs through Haze's work. If hip-hop's most fundamental maxim is to keep it real, she not only passes the test but redefines it. Over the six mixtapes she has released to date, she documents and dissects her inner life with dexterous skill and intelligence – from gothic fantasies so dark that Haze's producer nearly downed tools (he couldn't see God in it and tried to get her to change the line "don't scream, don't ask for God" before he'd continue working on it, but eventually backed down) to evocative outpourings of deeply felt love poetry to ruminations on sexuality and religion. (Haze is a self-confessed hopeless romantic: "I'm really obsessed with the idea of love. I have this desire to have this immaculate form of love that really doesn't exist, so my obsession goes on through life and I never find it and I end up miserable. But it makes me a better writer.") When she turns her hand to more traditional battle raps, the ferocity with which she shreds her foes is lent extra significance by her experiences.

Not that Haze is solely defined by her intensity. When we meet in London she rapidly switches between flippancy and seriousness – a technique likely designed to keep people on their toes. Describing herself as both a "super-sarcastic big bitch" and "really awkward to meet", Haze cracks jokes that you're not quite sure are jokes about the strip clubs she wants to visit later ("I want those hos naked!" she declares before the interview has even started), and dissolves into laughter when describing her rapid-fire rapping technique ("You have to train your mouth to move and your jaw not to lock").

As a teenager, she posted a video on YouTube called How To Give No Fucks – essentially a step-by-step guide to building up a defence mechanism involving sarcasm, blank facial expressions and a solid dose of self-help. You get the impression it has been put into practice a lot.

Now signed to a major label and working on her debut album proper, the Detroit native – voted third in the BBC Sound of 2013 poll – is becoming a legitimate force in rap despite her unlikely background. Born Raykeea Wilson, not only is she gay (she describes herself as pansexual) and mixed-race (she taught herself Tsalagi, the language of her Native American forebears), but she was raised within the traditions of the Pentecostal Greater Apostolic Faith, a church that Haze now describes as a cult. "We all lived in the same community, within 10 minutes of each other," she says. "You weren't allowed to talk to anyone outside of that, you weren't allowed to wear jewellery, listen to music, to eat certain things, to date people … you weren't allowed to do pretty much anything. Church was on Sundays, Wednesdays and Fridays. When they did revivals it was every

day. I used to just crawl under the bench and try to sleep."

The resentment she now feels is reflected in the religious imagery with which she peppers her most thrilling raps. "I'm challenging saints, and beating they fuckin' asses with the bibles they came with," she spat on an early freestyle on Kanye West's Monster. More concisely, she declared, "I'm Satan, and I'mma take your ass to church now," on last year's New York.

"I think of religion as something that stains the person," she says. "It's a mindset you can never get free from, it's always in the back of your head. Even mine! I think, am I going to hell for this? Then I have to remind myself that I don't fucking believe in hell!" Haze laughs again, even more uproariously.

Does she enjoy saying things others might find blasphemous? She leans forward, eyes flashing: "I thrive off that shit."

When she was 15, she escaped from the church's clutches after her mother fell out with its leaders and they moved to New York City. Unsurprisingly, she found it hard to relate to classmates at school. "It's the worst thing ever," she says, remembering a particularly excruciating incident involving a milkshake and her ignorance of the Kelis song with that title. Now, she is more sanguine. "The first Biggie [Smalls] song I heard was, what, a few months ago? Peter Rosenberg [hip-hop DJ at New York's Hot 97 station] played it to me live on air to embarrass me. I can't remember what it was." But was she embarrassed? Haze laughs contemptuously and emphatically. "No! When I first got signed, I read that Angel Haze shouldn't be a rapper, because she only started listening to music four years ago, she doesn't know anything about rap and she doesn't have enough credentials. That's how most hip-hop heads think, though. Bullshit."

Angel Haze performs at the Hoxton Bar, October 2012. Photograph: Robin Little

Haze's refusal to play along with the rap industry's expectations is refreshing, although she has been drawn into a well-publicised Twitter storm involving fellow up-and-coming rapper Azealia Banks. Insults of increasing viciousness flew back and forth – revolving around the question of whether Haze, as an outsider, had any right to record a song called New York – before the pair then traded swiftly-recorded diss tracks.

When we first meet a few weeks earlier, she sighs when she speaks about rap beef: "A lot of it is male rappers pitting female rappers against each other. A lot of it has to do with female rappers and their insecurities, wanting to be the only one because people have gotten accustomed to seeing that. It doesn't have to be like that. There isn't 'the' male rapper, there are all these dumb niggas out there rapping about dumb shit. Why can't girls have that? I don't partake in it. I've seen a lot of stuff in the press about Azealia and I being, like, friends and whatever … I just have a genuine respect for any female rapper, even the ones I don't particularly think are good."

When we speak again in late January, she sighs again. "Most people will never know the whole story or the truth behind [what happened with Banks], so for me it's dead and done and in the past. I don't have any problems with anyone." Later that week, she takes once more to YouTube to apologise for being a "bully".

However, more intriguing was Haze's calling out of Lupe Fiasco on the same mixtape that featured Cleaning Out My Closet in October. The original version of Fiasco's track Bitch Bad (from last year's album Food & Liquor II) saw the rapper attempting to stand up to misogyny, while only digging a hole for himself by blaming women for it. Haze flipped the narrative, detailing exactly how boys and men are shaped by, and end up perpetuating, anti-female attitudes. "Yes!" she exclaims. "I had to embarrass Lupe Fiasco because he did it all wrong. He did the woman-shaming, 'It's your fault, bitch' thing. The feminist in me wouldn't let this live. For me, it was important to portray what he couldn't."

Was the choice of the Eminem track motivated by similar feelings, given the prevalence of sexual violence in his material, or was that a tribute to his confessionalism?

"No. I love Eminem for the fact that he uses violent sexual imagery. People don't really get the extent that Eminem's music is emotionally driven. For me, he is clear from my line of fire because I love everything he's done."

It's the kind of statement that might seem inconsistent with Haze's feminist beliefs but she doesn't seem conflicted. She condemns rappers who trade on rape jokes for mere humour, and thoughtfully muses on the logistics of taking offence. "I feel like my [Native American] heritage isn't important … until I see shit like Gwen Stefani's video." The reference is to the No Doubt video for Looking Hot, in which Stefani wore an eagle-feather plume and a leather fringe designed to portray a Native American woman. "I didn't have a problem," Haze continues, "but then you see white people in America discussing it and saying: Oh, the 'Indians' are mad about nothing. And they don't understand the significance of what she did, how she made us look."

She shrugs, and refers to How To Give No Fucks once again: as most members of marginalised groups realise, this is often as imperative as fighting back.

A few weeks later, the issue of rape culture is dominating the media following the gang rape and murder of a 23-year-old medical student in Delhi and allegations of a coverup in an alleged gang rape in Ohio.

Speaking on the phone, Haze says: "People say, maybe you shouldn't have worn such a short skirt, instead of, maybe you – as a male – shouldn't have raped. And even though it's so prominent in our culture – stories every day! – people always say: You're lying. Every rapist is quick to tell the victim: Nobody's gonna believe you. When I finally told someone, they did nothing about it, and that's the worst thing of all."

Haze recently found some old photos on Facebook that brought this home to her: of her, pictured with Jerry Sandusky, the former Pennsylvania State University assistant football coach, on a college open day. "He was cool and paternal and took us everywhere. To the Skybox at the stadium. To the fucking locker rooms, where it happened." Sandusky was convicted last year of 45 charges of sexual abuse of young boys over a 15-year period.

Neither of Haze's rapists have ever been convicted. "Yet everyone seems to know," she says tightly. "I want to say I want to bring a case, but I honestly don't know how or where to begin. They'll say, it doesn't matter any more. It was 10 years ago. They'll say it was too long ago."

She trails off, and starts talking about her forthcoming album. "I'm taking my time to craft this, because you only ever get one debut album and you're judged on it for ever. I want it to be perfect." It doesn't sound intentional, but it's an echo of how Haze's Cleaning Out My Closet ends: "I made it through everything, I made you look like a clown / I'm fucking great, can't fucking hate you, nigga: Look at me now."

Angel Haze intends for the whole world to look at her as a great, not as a victim: the best revenge.

Angel Haze's mixtape Reservation can be downloaded at whenitraeens.com

Her UK tour dates are: 7 May, London Scala (Sold out); 8 May, Brighton Concorde 2; 9 May, London Heaven; 10 May, Birmingham Library; 11 May, Manchester Ruby Lounge; 12 May,Glasgow ABC 2.

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