Janet Mock is talking so fast I can’t keep up. One moment we are in Hawaii and she is living, desperately uncomfortably, as a little boy called Charles. The next she is 10 years old and has created the alter ego Keisha to enable her to talk to boys on the phone. Then she is living happily as a transgender girl, a star pupil and captain of the school volleyball team. Now she is 16, doing sex work and stripping at a local club to earn enough money to pay for her operation – or bottom surgery, as she calls it.

It is an astonishing story – and we have barely started. There is her move to New York at 21, a master’s in journalism, two bestselling memoirs, a groundbreaking drama she co-scripted and two marriages – and, along the way, she has become the world’s most prominent trans activist. Phew!

Mock used to call herself the great pretender. When she left Hawaii to go to New York, she decided to keep her past to herself. “I had to pretend, or withhold parts of myself. Specifically my trans-ness. I had to pretend I was any other 21-year-old. Most of them had not transitioned or had to work the streets or in a strip club, and most of them were not already married. So much had happened by the time I was 21 that I just wanted to be normal and regular, whatever I thought that was.” She finally takes a breath. “Right?”

Blimey, I say, do you always speak so quickly? She laughs and apologises. “Oh, I’m so sorry. I’ll slow down. Yes, I do talk fast when I’m excited. And I’m excited because this is a new space in my career.”

Her sentences are regularly punctuated with the word “space”, perhaps not surprisingly for somebody who has had to fight so hard to claim hers.

Mock is fastidiously polite. At times, she sounds like an old-fashioned southern belle dreamed up by Tennessee Williams. In fact, she grew up impoverished in Honolulu. Her father, Charlie, is African-American and was a drug addict (she had no idea and was devastated to discover when she was young that neighbours knew him as “Charlie the crackhead”). Her mother, Elizabeth, is Hawaiian. The family was broken and dysfunctional, but loving in its own chaotic way. As a seven-year-old, Mock went to live with her father in Oakwood, California. Her father called young Charles a sissy. Mock says she was called all sorts when she was growing up – freak, faggot, tranny, the N-word.

She did not see her mother for five years until, at the age of 12, she returned to Honolulu, where she flourished. Her mother never discouraged her from becoming Janet (a name she chose after a friend told her she looked like Janet Jackson). “There were bigger issues in our family. My mom didn’t have the luxury of time and resources to micromanage any of her children’s lives.” It was a blessing, she says – wealthier parents might have paid for therapy to “right” her.

Mock was helped by the fact that gender is relatively fluid in Hawaii. The word “māhū” denotes a third gender. It is a pejorative for gay men and drag queens, but it can also have a sense of the sacred attached to it.

“My mom, growing up in Hawaii, saw trans people existing every day. She didn’t know they were trans. She was just like: ‘Oh, that’s such-and-such who lives on the street.’ It was the norm to have people who were not male or female; people who may be in the middle somewhere.”

Mock, now 35, splits her time between Los Angeles and New York. We meet for lunch at a stately hotel in West Hollywood. Mock is gorgeous – tall, curvy, with brown, almond-shaped eyes, a perfect smile and cheek-bones so high you could hoist a flag on them. Despite her sing-song voice, she is fierce and forensic in her arguments.

She orders a super-strong cold brew (coffee brewed for hours in cold water) and a steak dish and we return to her past. At 15, she began hormone treatment without telling her mother. Soon after, she started selling sex and stripping to pay for her $7,000 (£5,700) surgery. The only thing she regrets, she says, is doing a porn shoot to earn the final $1,500. “The sex work was private, but this was on record for the rest of my life.” In her first memoir, Redefining Realness, she wrote that she was “immortalising the one part of my body that brought me so much anguish”.

I ask when she started thinking of herself as Janet and she says it is a false premise; she always thought of herself as a girl who was cursed by biology. She knew she wanted sex-reassignment surgery, but that was not going to determine her gender. “I believed I was, and knew myself as, a young woman, even when I had a penis. It wasn’t as if I needed the surgery to confirm that for me.”

Was there any point at which she felt she could be complete without surgery? “I did not, but that’s just my experience. I know a lot of people who do, and that’s where the burden of representation comes in. I’m sitting here telling my specific story, but though I wasn’t comfortable with that, there are thousands of people who are, or thousands who don’t have access to the funds to have surgery.”

Mock often talks about the burden of representation. She might be regarded as a spokeswoman for trans women, but she does not pretend her experience is representative. For one thing, she was fortunate enough to be able to choose whether to disclose she was trans. Many trans women do not have that privilege – their appearance gives them away.

She has said that without her smile and her MA in journalism, nobody would have listened to her. “The ‘pretty privilege’ can give you access to spaces, just like your able body gives you access. But it makes impossible beauty standards for many other trans girls who are struggling with that right now.”

She argues that trans women obsess too much about being able to “pass”, but she knows it is easy for her to say. She, too, obsessed about that in the past – ironically, one of the things she found validating was one of the things she most despised: men objectifying her.

She drains her cool brew, and our main course arrives – steak, brown rice, vegetables. “Oh, my God! This looks really good.” She examines one of the vegetables curiously, and calls over Wayne, the waiter.

“Wayne, is this like a sweet potato?”

“It’s a carrot,” Wayne says. “A purple carrot.”

“Very good. Thank you, Wayne.”

She has a way of engaging with people and dismissing them with self-assured charm.

Facebook Twitter Pinterest Mock: ‘I was thrust against a white backdrop.’ Photograph: Philip Cheung/The Guardian

Mock says so much has changed in the trans world since she was young. She hopes few people today need to go to the lengths she did to fund surgery. Would she swap her story for a more sober version? “No. I would have my story,” she says instantly. Is there any time she would have swapped it ? “When I was living it yeah. Che-che-che-che!” She laughs loudly and uninhibitedly, as if clearing her throat. “I wanted a genie to pop up and grant me three wishes – to get all this over with, to have a financial safety net and to be comfortable. But I wouldn’t take anything from my experience because it built my resolve; my core. I fought for every single thing I have now.”

Was she putting herself at risk on the streets? Yes, she says, but just being trans is putting your life at risk. The statistics are shocking – more than 2,000 trans people were killed between 2008 and 2016, the majority in South America. In 2014, research showed that 46% of trans men and 42% of trans women had attempted suicide in the US.

Actually, Mock says, there was a great support network among sex workers. “The girls felt safe there. We took care of each other. You showed up, you knew who was there and how long she’s gone. We weren’t doing it in isolation. Now sex work had gone online so you’re by yourself all the time.”

When she left Hawaii for New York, three years after surgery, Mock chose not to reveal that she was trans. She embarked on a new life experience, described in her second memoir Surpassing Certainty. “If I had disclosed, it would have made people judge me, made them not want to be with me, made me an object, a freak show. I would have been the trans girl in the room. To reveal to a class of strangers the heaviness of my past was just too much. It’s inconvenient. The inconvenient truth! And I didn’t want to be inconvenienced. It would get in the way. I just wanted to go to school to get a job, and move on.”

She felt both freed and imprisoned. “The secrecy was hard to cope with,” she says. Mock also became aware of her blackness in a way she had never been before. In Hawaii, she was primarily identified as trans and “everybody was at least brown or tinted in some way”. At New York University, she was one of a handful of black students. “So, in Zora Neale Hurston’s words, I was thrust against a white backdrop.” She pauses. “I love Zora. She is THE Queen!”

Her progress in the publishing world was seamless. Before long, she was an editor and writer at People magazine. But she became bored. She realised she had a better story to tell than the celebrities she was interviewing. And she wanted to own that story. In 2009, she met photographer Aaron Tredwell, who was to become her second husband. “I started telling the people in my life and I was like: ‘Oh, this story is interesting because I’ve never seen it before. This is pre-Orange Is the New Black, pre-Caitlyn Jenner.’ And I was like: ‘I think I should tell my story.’ I’d never seen a young trans woman who was living and thriving in the world, and I was looking for that.”

Throughout the Obama years, she says, transgender rights improved considerably in the US, but now Donald Trump is determined to reverse that progress. Last July, he attempted to introduce a blanket ban on transgender people joining the military.

“There is a lot of rowing back on protections that the Obama administration put through: the guidelines for trans children in schools; trans-specific affordable healthcare; the military ban.” She says it is part of a wider general clampdown on rights for minorities.

Trans women have been questioned from more than one side of the political spectrum. What does Mock make of the continuing opposition from some feminists?

“I think it is rooted in the same thing they say they’re fighting against – biological essentialism. So, it’s saying that if you don’t have these specific biological experiences as a woman you cannot be a woman, you cannot be in our struggle. I would argue that for women to say the only identifying factor of a woman is a pussy is misogynistic. If we’re saying that to be a feminist is to eliminate barriers and alleviate marginalisation based on gender, then how could you not want to include the persecuted trans women or non-binary folk so you have more comrades to fight against gendered oppression?”

She looks me in the face. “My grandmother gets who I am, so when you ask me about people who don’t understand, or people who are on their bully pulpits saying you shouldn’t accept people, I’m like: “What’s happened to you that, of all the things you can talk about, of all the injustices in the world, the one thing you want to concentrate on is trans people living their truth? How is that harming you and your identity? How I identify has nothing to do with you, and how you identify has nothing to do with me. Right? So live your life and let me live mine.”

She chews on her steak, decisively. I hope that is not directed at me, I say, cowering. She stops in her tracks and bursts out laughing. “Che-che-che-che. Nonononoo.”

Mock has spent much of the past year as part of the writing/producing team on Pose, the new trans drama devised by Glee creator Ryan Murphy. She is also directing one episode. I ask her what she thinks of Transparent, the US comedy-drama about a middle-aged father who becomes a trans woman.

“I don’t watch it, so I don’t know,” she says.

But it is one of the few dramas featuring trans characters, I insist.

“It was never really for me. Just because there’s a trans character doesn’t mean it’s a show I would watch.”

But I persist. Surely, if you are making a drama about trans people, you would want to watch what has gone before. “You’re really stuck on this Transparent thing, which is interesting to me,” Mock says, smiling. But, now, it is a hollow smile.

She quietly but firmly puts me in my place. “It’s about somebody way older than me, who was a professor. Transparent is about a white, middle-class, liberal family, so there are no intersections that interest me.”

Watch a trailer for Pose

What makes her so excited about Pose is that it is about the very people she knows and cares about. “Our show is centring on trans women of colour in a way they’ve not been centred on ever. What’s so radical to me is that, unlike Transparent, where there is one main character who is trans and played by a man, we have five main characters who are trans played by trans women. That five black and brown trans women will be the centre of a show on a network drama in primetime is huge. And they’re going to be on billboards. It’s amazing this is going to exist in the world.”

I tell Mock I have one final question, from a trans friend of my elder daughter. She asked: “How can a nice trans girl like me find the perfect husband like Aaron,” I say.

Mock roars with delight. “That is so sweet! What is her name?” Charlie, I say.

“To be in a relationship is an incredibly vulnerable space to be in, so you have to be willing to be open, to not be afraid of that intense gaze on you. Aaron was intense; he really wanted to know me. And I chose to show up as myself, and I chose to be vulnerable and tell him my story, and that has been the foundation of our relationship. We’re going to challenge one another by telling the truth to one another, then be strong enough to stick around when that truth is not exactly what we thought we were going to hear. I hope that helps Charlie.”

I’m sure it will, I tell her, and explain that Charlie is also an activist.

“What is her second name?” Charlie Craggs, I say.

“Oh, I know that name,” she whoops. “I’m not kidding. I follow her on Twitter.” Within seconds, she is searching her Twitter account. “Craggs? Cr … Cra … See, I told you,” she shouts, triumphantly.

Two cold brews down, and having just discovered Charlie, she is talking faster than ever. “I love that! It’s a small world. Shows how deeply connected we are! Che-che-che-che.”

This is who she has written her books for, she says – the next generation. Mock says she has done her bit: she can now go off and write screenplays and be a boring old binary trans woman. It is up to people like Charlie to take up the cudgels. “There are trans girls who are still navigating these spaces and wanting to learn and grow and they need something fun to look at when they see themselves. They don’t just need to know the tragedy and trauma of being trans. They also need to know how to better be, how to better live, how to better dream.”

Surpassing Certainty, Mock’s memoir will be published worldwide on 1 May