"I was pretty freaked out ... so we went to an emergency doctor the next morning, just to check. The doctor thought that it was most likely just a cyst, however he recommended I go for a mammogram and ultrasound when I got back to Auckland."
She had the tests the next morning, and a biopsy tissue sample was taken.
A day later she received the diagnosis that confirmed her gut feeling. She had an aggressive form of invasive cancer in a duct.
She had a mastectomy three days later, financed by health insurance, at a private hospital. The tumour was 2cm across, but no cancer cells were found in any of the five lymph nodes that were removed.
Chemotherapy followed, causing nausea, fatigue, peripheral nerve trouble and other side effects, and she is now taking Tamoxifen for five years and is part-way through breast reconstruction surgery.
And she is getting her life back on track after more than six months dominated by cancer.
"It's quite central to where I am at the moment. It's becoming less dominant (although) you always have it in the back of your mind."
Her mother was diagnosed with breast cancer at 37, and her father died of a brain tumour.
Genetic tests showed Miss Davis did not have breast cancer genes, but had an "undefined genetic variance".
Because of this, she is having ultrasound and MRI cancer check-ups every year. Her sisters, aged 20 and 21, are also having annual checks and her mother is having a genetic test.
Miss Davis chose to speak publicly to help other young women become aware of the disease.
"I wanted something good to come of my experience and I want to help educate younger women about breast cancer.
She also wants to highlight a fundraising campaign by the Breast Cancer Aotearoa Coalition that starts on Monday. The coalition intends to spend money raised to produce a support pack for women with breast cancer, a resource to help guide them through diagnosis and treatment.
Breast cancer*
All ages
• 2,759 cases diagnosed
• 665 deaths
Aged between 20 and 30
• 12 diagnoses
• 2 deaths
Aged between 30 and 40
• 137 diagnoses
• 20 deaths
*Female breast cancer, 2009 figures.
For four weeks from Monday, 20c from the sale of each packet of Tim Tam biscuits and each copy of Woman's Day magazine at Countdown goes to the coalition. If both items are bought together and the store's marketing card is used, 50c is donated.