However, she prefers to be called what the kids know her as - Nana Liz.
"It all started when I went to church one Sunday and I was asked if I could help take care of a baby whose mother was at the Bethany Centre in Grey Lynn. I thought, 'I can do that'," she said.
"Driving home with this baby, I felt quite honoured. Here was this baby whose mother had not yet met me and she was entrusting me with her child. I thought, 'I've finally found my vocation in life'."
She said there had been obstacles and hard times over the years but being able to give children a safe and loving home was what kept her going.
"Some people who do this might go on holiday and leave the babies to someone else, but for us they're part of our family and we all go on holiday.
"I want them to come here and be cared and loved - everybody wants to be cared for and loved.
"If I can do that, to make this child feel secure and loved, then that's my privilege and honour."
More than a decade after she took on that first child, Mrs Mills now has what she dubs "the wall of fame" at her home, with photos of nearly all of the children she has cared for.
Many are now teenagers and she still regularly sees some of her "babies" while out shopping at the local mall.
Mrs Mills said she was overwhelmed at being awarded a Queen's Service Medal, but was quick to share the honour with others who have helped her over the years.
They include her now-adult children, who grew up helping to make baby formula and changing nappies.
"It's actually given them an awareness that we don't always have a privileged life.
"We have dealt with many children who have been hurt and we all cry at the tragedy of that."
