"They laughed at me and told me I couldn't do it, so I went home and cried and said, 'I can't do it'. But I did do it."
The 32-year-old has proved there's very little she can't do when going after a seemingly crazy goal but it's difficult to appreciate where she came from when you look at her now.
Five years ago, she arrived in New Zealand from England "a little bit chunky" - she was 20kg heavier - after letting the party lifestyle take over. She knew she needed to curb the weight gain, so got back into cycling.
At this point, she decided she needed a nutty ambition - you'll find this is a common theme - so tried to find the hardest bike race in the world.
There are few tougher than Race Across America, a 5000km non-stop behemoth. Naturally, K2 sat nicely in this long-term ambition, in Hadley's eyes at least.
"It wasn't very nice at all [to hear someone say I couldn't do it]," she says.
"I still think about it a lot and it drives me. I don't want to be that fat person who people laugh at and tell me I can't do things. That's the reason I do most of the crazy things I do.
"I guess I'm glad that it happened. I got bullied in high school and that also drives me to be better now."
A lot of women don't react this way, with many citing fear of judgement or not being good enough as reasons to avoid participating in sport.
Progress is being made on this front and people like Hadley are helping address it at non-elite level.
She works fulltime at Hot Cycles in St Heliers and part of her role is community planner. She also leads weekly women's rides and works as a coach for women's athletes.
Most know her as Crazy Emma, the slightly unhinged cyclist who has names for all her bikes (Lemon, Tango and Lil Pink), but she's more than that to some.
"I didn't realise I inspired people until they told me," Hadley says.
"I sometimes look through my Facebook photos and see where I was and where I am now. I'm a different person.
"I always want to be the best at everything I do but I want to do everything.
"I just feel like not enough women challenge themselves as much as they should. They don't believe in themselves, which is what I used to do."
At her first attempt at riding the 160km around Lake Taupo, she actually turned around and started back towards an aid station to hitch a ride home before realising she was being ridiculous.
She finished and returned the following year to go around twice. ("I hated one lap, so I thought I would try two instead," she says.)
After that, she just had to go around four times. ("I had done two, so didn't want to do two again.")
The four-lap race didn't go well the first time in 2016, prompting her to pull out on the final lap.
She returned for a second attempt the following year, when she set a new women's record, but it took some doing.
She trained 18 hours a week on occasion, regularly getting up at 3.30am so she could fit it in around work and other commitments, and her training numbers were similar to an elite athlete.
"Those four laps, when I didn't finish, were hell. Absolute hell. I had to go back because I had a point to prove, massively. I'm sure there would have been people thinking I couldn't do it. In my head, I thought that, anyway.
"I had a year to train and I trained my arse off. It was really emotional when I set a new women's record and that's the thing I'm most proud of.
"I never thought I could ride that far in one go. Not many people can say they've cycled 640km in one go."
On the agenda for the remainder of the year is the amateur world championships in Italy, before tackling November's Pioneer mountain bike race when she will be part of the OFF & ON team.
Her Pioneer commitments, when she will race for six days around the Southern Alps, will mean she will miss Challenge Taupo, which might not be a bad thing considering she was threatening to attempt the eight laps race.
Some believe you need a little craziness to help keep you sane, and it probably applies to Hadley.
She still aspires to tackle the Race Across America and next year plans to compete in the TransAlps in Italy.
Few would now challenge her ability to do it but she might not have got to this point if she hadn't been mocked all those years ago.
"I would probably say to him now, 'thank you for being a dick and pushing me a bit harder'," she says. "And a whole lot more."
