The St Hilda's Collegiate School year 13 pupil has been rubbing shoulders with some of the world's high-profile female leaders during the past week, at the Women Deliver global conference in Copenhagen.
"You see these people on the news and in the papers and in all these reports on the high level, amazing things they're doing.
"But when you get to sit and listen to them talk as people, and hear their real opinions as they speak from the heart, you realise they're individual people who have gotten to where they are by pursuing their passions.
"They're here for the exact same reasons I am.
"That gives me confidence that I can be just like them.''
Casey (17) said the highlight of her trip was meeting Miss Clark, who is the United Nations Development Programme administrator.
"It was incredible. It's been a long-time goal to meet her. She's a real inspiration to me.
"Obviously, she's running for secretary-general, and she holds the highest office for a woman in the UN. She's blazing a trail for women to get involved in high-level jobs and international relations.
"I definitely want to see if I can follow in her footsteps and get a job in the organisation, too. She's a great role model.''
Casey said she spoke to Miss Clark about her bid for the UN's top job and her hopes for her campaign.
She said Miss Clark was "very determined'' to get the job, and while the business of election campaigning was mostly serious, there was a lighter side that she was enjoying.
"She whipped out her phone and started showing us pictures of funny mock-up T-shirts, advertising ‘Helen Clark for Secretary-general'. She sees the funny side of things.
"A group of us from New Zealand had some badges made which said: "Helen Clark for Secretary-general''.
"We gave her one and she was so taken with it she handed her phone to one of the other girls and said she had to have a photo taken with it, to put on Twitter,'' Casey said.
The conference was the largest in more than a decade on the health, rights and wellbeing of girls and women.
It brought together about 6000 leaders, advocates, policymakers, journalists, young people, researchers, and corporate and civic society leaders.
