The first time Elaine Welteroth came on to my radar was at a Thanksgiving dinner. American friends in London had invited me and I was torn between gratitude for their hospitality and deep reservations about celebrating something with genocidal undertones. So I decided to embrace the first and challenge the second, arriving with a chilled bottle of wine and a fully loaded YouTube video. A video from Welteroth’s Teen Vogue digital team.

It showed a group of Native American girls talking about what Thanksgiving means to them. “After every killing of a whole village, these European settlers celebrated it and they called it Thanksgiving,” says one. “I’m thankful to be indigenous, resilient and alive,” says another. To say it was a bold move for Teen Vogue – a publication once better known for lipstick tips – is an understatement. “Native American Girls Trash Thanksgiving for Teen Vogue,” said one critical website.

“That video was extraordinarily compelling and impossible to ignore,” Welteroth says. “You know Native Americans just rarely get the mic, or have their voices and their perspectives amplified. So it felt good to be part of a team that would actually make people stop, put their turkey down and rethink what they’re really celebrating.”

Listening to Welteroth’s reflections as we share a sofa in an airy London auditorium, it is hard to believe that we are already speaking about this era in the past tense. Having whirled the hashtag #BlackGirlMagic into overdrive when she was appointed the first black beauty director at Teen Vogue in 2012, Welteroth was appointed editor-in-chief of the magazine in 2017, aged just 29. It was a remarkable rise in a remarkable career – in under a decade, Welteroth had gone from intern at the African-American magazine Ebony to the youngest Condé Nast editor in the company’s 108-year history. Championed as “prolific” by Anna Wintour, Condé Nast’s artistic director and the editor of Vogue, Welteroth had helped in her previous role to increase traffic to TeenVogue.com from 2.7 million to 9.2 million unique visitors a year, with print subscriptions reportedly up 535% in a year. And then, just like that, at the end of 2017, Condé Nast announced it was closing down the print edition. “That wasn’t the vision that I had for the future of Teen Vogue,” Welteroth says. A couple of months later, she resigned.

‘My mom is from a generation where they don’t talk about their trauma’ ... Welteroth speaks at an awards ceremony organised by the magazine Essence in Los Angeles in February. Photograph: Rich Polk/Getty Images/Essence

The news made headlines, as the new – in some cases unlikely – fans of Teen Vogue, myself included, wondered how something going so well could go so wrong. Now, Welteroth is in London, ready to spill all the tea. Her book, More Than Enough, is part memoir, part career guide, part self-help journal. From the reaction I have seen so far on social media, black British women are ready and waiting for it.

“Being able to do these events and see how people react and what we do, what we talk about as black women … it’s like it is black female professional church,” Welteroth says of an event she did the night before we meet. “There are white people in the room, and there are men in the room, but you can really see black women are centre … it’s a hard thing to describe – a palpable energy. People cry. It’s like everyone is coming to the table with the same brand of PTSD.”

The combination of faith, energy and trauma is also a summary, of kinds, of Welteroth’s book. More Than Enough is peppered with anecdotes that illustrate the spunky, do-it-yourself attitude that helped fuel her rise – such as when her internship expired unnoticed, so she simply gave herself a new job title. “One day I got ballsy and decided to change the title in my email signature from Editorial Intern to Production Assistant. Boom, just like that: I got my first promotion, albeit fraudulent.” Then there was the time she challenged the decision of Condé Nast – delivered by Wintour – to promote her to editor-in-chief with an insultingly small and allegedly non-negotiable pay rise, asking: “Doesn’t this seem contradictory given that this company publishes stories every day encouraging women to advocate for themselves and to negotiate their salaries?”

Welteroth is clear that her rise would not have happened without a vision and a plan. Born to a working-class family in a predominantly white neighbourhood in northern California, she says her identity was shaped by growing up “biracial”, as Americans call it, with an African-American mother and a white father.

It is a complicated story that Welteroth unpicks in her book with patience and honesty, acknowledging the privilege that comes from being light-skinned in a world that penalises blackness and at the same time challenging the idea that there is one biracial experience. “I think there is something to be said of the difference between having a black mother and a white father,” Welteroth tells me, having established – with some excitement – that I, too, am a member of what she calls the “black mom club”. “I have always had a black woman model for me what a black woman looks like, how to move through the world as a black woman.”

I worked hard to get a dream job, then found out that I had become a black woman making history

Magazines played a role from the start in her understanding of the way race operates in the US, not least because of her early awareness of the absence of images of people who looked like her. “I write about being in pre-school, having no concept of race, and being handed magazines, being asked to make a family collage and finding no one in those magazines who is black, because I think it will help illuminate the nuances of racial tension and help simplify it,” she says.

The young Welteroth sought refuge in black magazines, especially the African-American titles Essence and Ebony, filling zipped bags with cuttings and building dramatic story arcs for the black women transformed in her aunt’s hair salon, whom she turned into characters inspired by the success stories she read about in magazines. And magazines played a deeper role in triggering her consciousness, too.

“Only as an adult, in quiet moments of reflection, can I begin to see clearly the subconscious impact of white supremacy at work in the messages I was fed as a child,” Welteroth writes. “By centring and positioning whiteness as superior, whiteness as the norm, and everything else as a deviation, a racial hierarchy is reinforced. I lived in a world that reflected this hierarchy I saw in the media. I grew up with an unspoken suspicion that the world would see me as second best, too.”

It is no surprise, then, that once Welteroth gained editorial control at Teen Vogue she got to work challenging this messaging with headlines such as “Donald Trump is Gaslighting America” and detailed features on cultural appropriation. But such is the complexity of race in the US that Welteroth’s mother – who is from the intensely racialised south – questioned such features. “My mom is from a generation where they don’t talk about their trauma, or about black identity in the way that we are intellectualising it,” Welteroth says. “So when I was going through the whole cultural appropriation piece, my mum was like: ‘You know, in my day, we didn’t have time to worry about no cultural appropriation. Girl, we were trying to get a job and keep a job. What’s that called? Survival. So you can go ahead and take that mess and take it somewhere else.’”

At the same time, Welteroth stresses that her parents have supported her work, and that her father has been her biggest advocate. “I think the stories in my book normalise interracial families. Why wouldn’t my dad be proud of his daughter, who is making an impact?”

‘I always had a multipronged media career as my long-term game plan’ ... Welteroth on Project Runway. Photograph: Karolina Wojtasik/Bravo/NBCU via Getty Images

Welteroth’s book does not shy away from her struggles, though, such as her father’s alcoholism, or abandoning her dream of studying at Stanford to follow a boyfriend to a state university, only to end up having to visit him in jail at the weekends, hoping her classmates would never find out. It is the kind of decision from which a middle-class kid would been steered away firmly, but Welteroth – the first person in her family to go to university – learned many of her lessons the hard way.

It took her a while to see the bigger picture of her achievements. “I write about feeling like a bit of an accidental activist,” she says. “I didn’t walk to the table with my fist up. I was a 25-year-old black woman who worked hard to get a dream job, then found out in the headlines that in fact I had become a black woman making history.” This was part of why she wanted to write her book. “Because the headlines just made it seem like I was a sort of token black hire, which feeds into this magical negro complex, right? All you need is one token black person and then they can transform the whole thing. And I don’t want to be a part of selling lies about success.”

As such, she seems to have gone out of her way to speak openly about her mistakes – such as an article she ran celebrating Afrocentric hairstyles, but featuring only light-skinned and white women. “How could you!” wrote one person on Twitter. “Why’s your magazine so anti black?” wrote another. Welteroth shudders when I ask her about this. “I had wanted to really celebrate Afrocentric beauty by writing about how it is actually a form of activism. And then I realised that, even as a black journalist, I had blind spots, and I had to learn how to be an advocate for my community,” she says. “I want to dispel any myth that just because you’re black and you’re in the room it means that you’re fully equipped to represent your entire race. That is a fallacy. Everyone shares the responsibility of learning how to talk about race more responsibly.”

It was not perfect, but there was no mistaking what Teen Vogue became under Welteroth – a conscious voice, tackling the fraught terrain of our culture wars with nuance and intelligence. “We were the underdog in a larger media conglomerate … and I don’t think there were great expectations for the future of a brand like Teen Vogue,” Welteroth says. “So I think our strategy was don’t ask for permission, be prepared to ask for forgiveness, and march forward letting your instincts guide you.”

Would the powers-that-be at Condé Nast have sanctioned the progressive content that became normalised during Welteroth’s time at Teen Vogue had they known what was coming? “There weren’t a lot of eyeballs on what we were doing day to day,” Welteroth says. “Once it hit a fever pitch, the reception was overwhelmingly positive – and there were business results attached to it, you know; our traffic soared. But, in truth, I think it would have made people really nervous if they were invited into the decision-making process more.”

‘I’m at the beginning of an exciting new chapter’ ... Welteroth with Yara Shahidi on Black-ish. Photograph: Eric McCandless/Walt Disney via Getty Images

Welteroth’s disappointment with the way Teen Vogue’s rise was rewarded – or not – is palpable. But she did not miss a beat, turning to her role model and mentor, the editor, author and all-round media phenomenon Harriette Cole, who hired her at Ebony. “I always had a multipronged media career as my long-term game plan. I knew, like Harriette, that I would start with magazines, build a strong foundation and then eventually I would need to take a leap of faith and build on the different parts of my media career.”

That plan saw Welteroth become a judge on the US reality show Project Runway and a writer on the sitcom Grown-ish – a spin-off of the hit show Blackish, in which she made a cameo as herself. She is now in the process of writing more scripts for TV. “I spent a week in the writers’ room – it was like a crash course in TV writing,” Welteroth says of her time writing on Grown-ish. “It was such an amazing experience; I’m at the beginning of an exciting new chapter.”

There is an undeniable buzz around Welteroth. This is not hindered by her appearance, which – like everything else about her career – is intentional. She is wearing a mesmerising suit in varying green checks; flawless, efficient makeup; and her trademark curly hair. In the book, she writes that this was inspired by advice from Cole. “Harriette [Cole] always told me every notable editor has a signature look, and my big, curly hair would be mine,” she says.

Comparing Welteroth with Wintour – the most notorious owner of a signature editor look, with her austere, decades-strong bob – it is less surprising that her path has been different. Unlike Wintour, the career editor, Welteroth sees herself as someone who was privileged to be steering Teen Vogue at a moment of change. “The transformation that happened at Teen Vogue, the politicisation of the content, was inspired by the audience that we served,” Welteroth says. “There was this awakening happening, I think, across the world; Teen Vogue seemed to capture that consciousness.”

What Welteroth did in that moment was historic for magazines. But, listening to her plans, it is no surprise that a magazine was not enough to contain her.

• This article was amended on 4 November 2019 to note that the Thanksgiving video was produced by the Teen Vogue digital team; to make clear that Welteroth’s mother supports her work; and to remove an incorrect reference to the article about Afrocentric hairstyles being a cover story.

More Than Enough by Elaine Welteroth is published by Ebury Press. To order a copy for £13.19 (RRP £14.99), go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £15, online orders only. Phone orders, minimum p&p of £1.99.