Mrs Peden was shocked to find a lump in her breast, and went to her GP to get it tested.
She was diagnosed with grade three triple-negative breast cancer - a particularly aggressive and hard-to-treat cancer. She was 48.
Mrs Peden said it was initially very hard to comprehend that she had it.
"I was under 50, and I'd had three children and I'd breastfed them, and there was no family history. All those things that you think would be contributors, I didn't have."
She was not due for her next mammogram for another eight months, and it was likely the "very rapid growing" cancer that she had could have spread further by then, Mrs Peden said.
"Who knows what a difference eight months can make."
She underwent a mastectomy in June and chemotherapy after that. After checks every three months since then, she is "so far so good".
According to the New Zealand Breast Cancer Foundation, around eight women a day (3000 a year) are diagnosed with breast cancer, and the disease claims about 650 lives a year.
Mrs Peden says if it was not for the breakfast she was invited to, she would not have been prompted to do the self-check.
"Had I not known about it at all, I wouldn't have done it."
She said lots of positives had come from her cancer scare in terms of awareness, including a head shave fundraiser at the kindergarten she works at in Swanson.
Mrs Peden has since made it to two Pink Ribbon breakfasts - one at the same friend's house last year and another at her parents' retirement village. She said she was planning to go to one again this year and was motivated to spread the word.
"Initially I didn't really want to, you know. You go through that thing of not wanting too many people to know what's going on.
"But then you think about the bigger picture and I have no problem telling people my story now because you know what they say - if it helps one person, some good has been done."