''Indebted'' to the health professionals who treated her ''so well'', she has now recovered and is raising funds to improve the environment for cancer treatment at Dunedin Hospital.
''I found everyone extremely professional.''
It was ''horrible'' receiving the diagnosis in January 2014, Ms Day-Cleavin said.
''My experience was seamless.
''From the bad mammogram result, I had everything I needed in place within seven days.''
When she saw an advertisement in The Star about the Southern Blood and Cancer Service being chosen as a beneficiary of the Dry July alcohol-free challenge, she decided to take part.
So far, she has raised more than $800.
Ms Day-Cleavin (40), who had four tumours, had no family history of breast cancer.
She urged women to follow their intuition if they noticed a change.
Her GP was supportive and referred her for a mammogram, but did not think the small lump Ms Day-Cleavin detected was likely to be dangerous.
''One of my key things about the whole experience was having faith and trust in your own intuition about how your body changes.''
The money raised by the Dry July challenge would be spent on new chemotherapy chairs, patient gowns, and upgrading waiting and patient areas.
''It's trying to make life just a little bit easier for those who are undergoing these treatments.''
Ms Day-Cleavin was not a heavy drinker, but the challenge had made her think about her relationship with alcohol.
Her husband, Chaim, is supporting her by giving up alcohol too, although he is not taking part officially in the challenge.
Weekends were the hardest, as a glass of wine with a meal signalled the end of the working week.
''Once you push through that ritual and the habit of it and challenge that, it's remarkably easy.
''I wouldn't describe myself as a heavy drinker but it certainly challenges the way you think about your habits and perhaps your relationship with alcohol.''
