Entry into the exclusive club was by invitation only.
The rules were simple – cut yourself, and then share a picture on social media.
The girls were 11 and 12 years old.
When Frankie* found out about the club, she was livid. She wanted to know what her daughter's school was doing to shut it down. She says the answer was vague – if it's not happening on school property, they said, there's nothing we can do. Soon after, an item about cyber-bullying appeared in the school newsletter.
Frankie knew her daughter had been having some trouble with some of the "cool" girls. "I kind of fobbed her off, being like 'Oh, girls will be girls, they're just being bitchy.' I said: 'You've just got to be you, don't worry about what they're saying.'"
It was the school that told Frankie her daughter had been cutting herself. Alone, in her bedroom at night. One of her daughter's friends confided in a teacher.
"It's not anything I ever saw coming," Frankie says. "You don't ever expect your kids to do this, do you? It's like, really?
"I think she viewed this as an option, 'I'm not feeling good about myself and I'm gonna do this.' They're all looking for validation among their peer group, and on the internet.
"I try and tell her: 'What you see on the internet isn't real. How many times do you think she had to take this photo to get 123 likes?' But she thinks she's a big girl, and she's starting to have boys look at her, and that's the other problem."
Frankie was shocked to discover her daughter, then 12, was self-harming.
Sadly, maybe she shouldn't have been. Research has found self-harm among young people is common: almost a third of New Zealand teenagers report hurting themselves intentionally at least once.