Que's mother Ariane Wyler arrived in Australia last night, on a flight from Switzerland.
Wyler was concerned that Langdon would head off again with her daughter and "he'd never be found again", according to Child Recovery expert Col Chapman.
Chapman said Wyler observed Que from afar last night and then approached her this morning.
He said Que was very happy to see her mother.
"It was as though she had just spotted Santa - she couldn't believe it. She was all smiles and very, very happy."
The pair had breakfast and are now playing in the park.
Langdon said on arrival in New South Wales on Wednesday that he had planned to sail to the Bay of Islands for Christmas, a journey that might take a week. The plan went awry on the fourth day when one of the small yacht's two rudders broke.
He had materials aboard to repair the rudder but the weather didn't allow him to do so.
"The wind kept pushing us off shore and the sailing I was doing wasn't effective at getting us towards New Zealand."
He said he made the decision to head for Australia on about January 1. "We were pretty much blown here. I had limited choices in the angles I could take."
Langdon denied he sailed from New Zealand to Australia to avoid an ongoing custody dispute between himself and Que's mother stating he has been Que's primary carer since birth.
"It's not a custody battle, it's an access thing," he said. "I've always been looking after [Que]."