The Dunedin student was diagnosed with Hodgkin's lymphoma when she was 14 and yesterday spent time at the New Zealand Blood Service Dunedin donor centre for World Blood Donor Day.
Being told she had cancer had been a "big shock" and she was quickly "thrown into treatment".
Over four months, she received chemotherapy, radiation therapy and blood transfusions.
The blood treatment started straight away, with the first of nine units given to her then to replace red corpuscles lost to the cancer.
Six years on, she was in remission, and grateful for the treatment she received: "I don't think I'd be here otherwise," she said.
Miss Millichamp wanted people to understand the importance of donating blood, and the wide range of reasons it was needed - from saving victims of car crashes to treating cancer patients.
Nationally, new donor numbers were down an unprecedented 18%.
In previous years, more than 21,000 people donated blood, but this dropped to about 17,000 last year.
New Zealand Blood Service marketing manager Paul Hayes said the national drop in new donors was a "worrying statistic that we want to reverse now".
This year, more than 42,000 people will need blood, or blood products, to help save their life.
To meet demand, the service needs 3000 donations a week and relies on existing donors.
"Every donation made can help save up to three lives," Mr Hayes said.
