"He let me kiss him on the cheek but then I went in for it. The rest was history," she said afterwards.
"It was everything - I'm very happy. I reminded him it was the third time I asked (him to marry me)."
Prince Harry arrived at the Sydney Opera House to greet hundreds of fans on Thursday morning as his month-long Australian military deployment comes to a close.
Wearing army fatigues and a black beret, the fifth in line to the throne stopped and talked to the group of pupils who had gathered excitedly on the Opera House steps to meet him.
He asked them questions and told jokes as they laughed excitedly. Harry even called out to one young female teacher who came down for a hug, much to the delight of her students.
He then greeted waiting fans, some holding signs including, "Marry me Harry", "His Royal Hotness" and "Gingers Rule".
The prince chatted with fans, stopping for photos and shaking plenty of hands.
He good-naturedly refused a hug from royal fan Megan Santamaria, 22.
"I'd have to hug everybody!" he said. "I'm not going to shake your hands!" He joked while flashing a smile at photographers as he walked past the press pen.
Elizabeth Stanley, 18, asked Harry for a selfie but he refused. "No, I don't do selfies," he told her.
Gallery:
Image 1 of 13: Prince Harry meets members of the public during a visit to the Sydney Opera House on May 7, 2015 in Sydney, Australia. Photo / Getty
She then asked if her friend could take a photo of them both, and he happily obliged. "Maybe you can photoshop me in!" he said.
Prince Harry starts his tour of New Zealand on Saturday in Wellington.
Prince Harry's NZ visit
Saturday, May 9: Wellington • Arriving in New Zealand, greeted by Governor-General at Government House.
• Visiting the National War Memorial and Anzac Square.
• Attending Hurricanes vs Sharks Super 15 rugby match, Westpac Stadium.
May 10-11: Stewart Island • Meeting locals and travelling to Ulva Island, a Department of Conservation open island sanctuary.
May 12: Christchurch • Visiting the Quake City exhibition, mall, and meeting student volunteers from Canterbury University.
May 13: Palmerston North • Visiting Linton Military Camp. He is to be taught the Army's haka.
May 14: Whanganui • Visiting Putiki Marae. He will join the crew of the marae's waka for a trip on the river. He will also visit the war memorial centre to meet local veterans.