As a child, Cullen would read letters to the editor, dreaming up a fantasy world "in which people got to swan around and meet celebrities and have a thing called the beauty cupboard that had free Bonne Bell in it".
But the magazine industry was very closed off for people like her, who grew up in the suburbs without any contacts, she told Jesse Mulligan.
"While I dreamed of making it, I don't know that I ever believed it."
Even when she'd been an editor for 10 years and could strut around as if she owned the place, Cullen says she still had moments of disbelief.
Her entry into the world of magazines was a mixture of hard work and an unlikely connection.
"I had been slaving away at work experience for my entire senior schooling career and I'd show up after holidays and I was just lucky that I was in reach of these magazines ... but at the same time I just happened to be dating someone who was very connected in the magazine world."
Cullen got her first break when her high school boyfriend was asked by an editor to MC an event for a magazine on the same night as her Year 12 formal.
"The only way that she could get him to do her event instead of coming to my formal was to make me an employee."
While she didn't want that to be her story, she knows she'd put in the hours, working as an unpaid intern.
She says as an editor she always made an effort to hire those who were the most passionate and hungry for the job. She wasn't interested in hiring people solely based on connections.
Did she ever work for a "Devil who wears Prada"?
"Yes, I did,' Cullen says. "It's impossible not to in this industry."
Magazines are not a democracy, she says. "Only one person lives and dies by the sword. If a magazine cover fails or it's not selling, it's only the editor who loses their head."
Naturally, that means people who enjoy playing God end up in those editing positions, she says.
In the early days of retouching, she says she was asked to lighten skin tones and put heads on bodies they didn't belong to. She feels lucky enough to be part of a change and push for less retouching in magazines.
"And also, to be part of a new breed of editors who were able to push for a different kind of cover girl. I think when I first started it was very much about a pretty, skinny blonde who you saw on TV every night and that was what sold."
That changed when social media became popular, with people wanting to see themselves reflected on magazine covers and women who had achieved great things rather than just looking beautiful, she says.
Growing up, Cullen wanted to be the cool girl, who wasn't bothered by anything.
"It wasn't until the MeToo movement that I really grappled with some of those incidents that before I think I'd put down to just stuff that happens to girls or stuff that boys do, and I really began then to look at things in a whole new light and to understand the ways that some of those things affected me."
She talks about them in the book and says while you might walk away physically intact, "a little bit of your soul has been destroyed in the process".
"For me it just really shone a light on how many of those instances I had and how I wasn't unusual in having that sort of volume, that every woman I know was experiencing these things all the time."
It was a powerful movement for women, she says.
"This has changed how we are as a society and a culture; it's changing slowly but it's happening."
Cullen has four boys.
Able to speak in front of a boardroom of scary suits, she says she doesn't know why, but put her in the playground for the school pickup and she is an 11-year-old girl again, terrified of the cool kids.
"I think a lot of women feel that way, I think the school pickup - particularly for working women but not only - can be incredibly intimidating."
Eventually, things started to catch up with her.
"From a work perspective, I only had one dream since I was 14 years old, I had achieved it and then I was plodding along and feeling like it wasn't quite fulfilling me, but I didn't know any other way."
After turning 40, she felt she needed to start living her truth and start telling her story.
"And so I made the call to leave my job and also to leave my marriage and it was a tumultuous couple of years but even at its toughest, even at times when I was most broken and on my knees and feeling like I was making all of the wrong decisions on one level, my gut always felt like it was doing the right thing."
She felt a calm come over her, for the first time in her adulthood.
"The payoff is here now and I've never been happier."
- RNZ
