Over the course of three seasons of Issa Rae’s HBO comedy, Insecure, Natasha Rothwell’s character Kelli has emerged as the breakout star, the DGAF member of the central girl-gang foursome.

“She’s the only character on that show who’s not obsessed by a man, getting a man, or getting over a man,” notes Natasha Rothwell over the phone from LA. She’s also the only one getting fingered under the table in a restaurant.

Earlier this year, the website Refinery 29 even published an online guide to Being a Kelli: (“We’re thinking Kelli binges on something unlikely before going to bed, like Snapped, the series about women committing murder”).

“She’s a version of myself I very rarely get to be,” reflects Rothwell. “I equate it to volume. In real life, I’m the most comfortable when [life is] dialled down to a two, while Kelli lives with that dial all the way past 11. It’s cranked up and that’s just where she thrives. So when I get to play her, it’s so freeing,” she continues. “You get to step into a person who lives without fear, and who isn’t afraid to make mistakes and who understands what it’s like to live in a world that never questions her validity in any room.’

Picture this: (from left) Molly, Issa, Tiffany and Kelli in Insecure. Photograph: Lisa Rose/HBO

This is a central part of what has made her such a fan favourite: her refusal to apologise for being herself. “So often with my early experiences with characters of colour onscreen, they first had to reconcile their race and then reconcile their gender before stories were allowed to be told about them,” says Rothwell.

Insecure, by contrast, is “a story in which we’re allowed to have this group of women of colour in south LA with very regular problems”. Or, as the show’s creator and star, Rae, herself puts it: “a show about black people being basic”.

Hired initially as a writer on the show, Rothwell began learning Kelli’s part at table-reads after the character appeared a little way into the first season, and Rae and Prentice Penny, the showrunner, offered her the on-screen role, too.

Being both actor and writer, Rothwell has a comprehensive take on the show’s most debated storylines, which include that of the now-infamous “blowjob episode” in season two. Criticised in some quarters as regressive, and feeling out of step with an otherwise radical and progressive show, the episode featured the four female leads discussing their stance on blowjobs. Kelli doesn’t do it, Molly does, but only in a reciprocal arrangement, while Issa finds them “too intimate”, and believes they make black women seem disposable.

“I stand by that storyline,” says Rothwell, equably. “We’re this new fresh take on black storytelling, and when people don’t see their specific storyline they think you’ve missed the mark.” Again, she believes the solution is a somewhat simple one. “If you don’t see your story being represented or told in the way that you’ve experienced it, then pick up a pen. Get behind a computer. Write your story.”

Writers’ rooms have traditionally been overwhelmingly white and male, creating inevitable problems when it comes to crafting diverse and specific storylines. By contrast, eight out of 11 members of the Insecure writers’ room are black and female. “I’m surrounded by more black women in my writers’ room than I have been in my writing and performance career combined,” says Rothwell.

Born in Wichita, Kansas, Rothwell spent her childhood moving around the US because of her father’s job in the air force. “I got my period in Maryland, so that feels like a significant place to say that I am from,” she quips. “My sense of humour definitely lubricated many a situation in a new school and I was able to understand people; I read people really well now.” The youngest of her three siblings, and the only boy, her brother shares her sense of humour, beginning a Christmas tradition some years ago of wrapping up a pair of his dirty socks in luxury paper as a gift for one of his sisters each year. “Whenever it was my turn to get the prank gift, I was just totally ruined because it looked so beautiful and I was so excited,” Rothwell recalls.

These days, she says, in a stand against rampant commercialism, her family exchange cards instead of gifts. “Two years ago, shortly after the 2016 election, my mum gave me a card with a printout of a quote from Hillary Clinton that said: ‘Never stop believing that fighting for what’s right is worth it.’ I bawled, because I really needed to hear it,” she says.

After studying “really serious drama” at university, she says it took a professor to point out that she was resisting a natural talent that “people would pay money to have”, and encouraged her to pursue comedy.

In New York, she began working the comedy scene in the evenings while teaching high-school drama during the day, and was eventually invited to audition for Saturday Night Live. In a bid to tackle its very public and much-criticised diversity problem, SNL had invited only women of colour to this particular audition. “Backstage was like a black woman utopia,” says Rothwell. And, from that pool, it hired Sasheer Zamata – the first black female cast member since Maya Rudolph left in 2007, Leslie Jones and LaKendra Tookes as writers and, a short while later, Rothwell.

Natasha Rothwell in Insecure. Photograph: HBO

On the subject of SNL and diversity, she says that “with any institution as respected and long-revered as SNL, with a 40-year history, there is an issue of trying to figure out how to walk that line of transitioning tokenism into true inclusion”.

“I think they’re really working hard to tell different stories by who they’re hiring,” she says, pointing to the recent hiring of writer Bowen Yang, and Awkwafina hosting – only the second Asian American ever to do so.

However, for all the show’s efforts at inclusivity, she simply didn’t feel at home. She quotes the poet Yrsa Daley-Ward, and her one-line poem, Shape: ‘‘If you have to fold to fit in, it ain’t right.”

“I’m a natural people-pleaser, and I was trying so hard to figure out the key to success there, but eventually I realised that I needed to figure out the projects that fitted with me.” She walked away from Saturday Night Live following just one season. Shortly afterwards, however, HBO came calling. The channel is now backing Rothwell enthusiastically; along with Insecure, she has her own development deal, and is working on a “subversive” comedy for the network, set in New York.

Meanwhile, she has also landed a role in the forthcoming Wonder Woman 1984, about which, sadly, she can reveal nothing. “I’ve signed so many NDAs, I’m sure I owe them a child,” she laughs.

“I would love to tell the twentysomething me in New York – working at a high school during the day and hitting the comedy clubs at night – where it’s all going to take her, because it’s truly mind-blowing,” she says. I can practically hear her beaming at the other end of the line. “I wake up most days and I’m just like: ‘Holy shit, this is my life.’”