She guided the New Zealand under-21 side to victory at the world youth championships in Glasgow in the weekend.
The Australians were favoured to defend their title but were upstaged by New Zealand 52-47.
''I guess all the hours and the time put into the campaign, not by just me but a lot of people behind the scenes ... has really paid off,'' Southby said.
''The resources they [Australia] have is quite significant in comparison to what we have. But I think we were smart in how we did things.
''We played them last year and they beat us. But we knew by the end of the series that we had the wood on them in the sense some of the things we were trying, from a game-plan perspective, were working.
''We just had to get better at executing and that is where the focus has been over the last year.''
Southby left nothing to chance and certainly did not shy away from making the tough decisions.
Former Otago defender Zoe Walker and Steel defender Phoenix Karaka got the nod for the final which meant captain Storm Purvis had to watch from the sidelines.
It was a big call but Southby believed it gave her side the best opportunity to win.
''Look, it is never an easy thing to do and I guess it wasn't easy on Storm either. But the reality was Zoe and Phoenix had developed a pretty strong combination.
''Storm was on fire and ready to go if we needed her to. But Phoenix brings a really strong attacking element to her game and that is what we needed.''
Purvis' Otago team-mate, shooter Te Paea Selby-Rickit (21 from 22), and Dunedin-based wing defence Stacey Peeters had cracking games in the final. The trio are taking the opportunity to have a holiday while they are in that part of the world and have not returned to Dunedin as yet.
New Zealand breezed through pool play recording heavy wins against Bermuda (107-16), Malta (94-6), Northern Ireland (102-15) and Trinidad and Tobago (77-16).
Wales was dispatched 79-41 in the quarterfinal but Jamaica gave New Zealand a fright in the semifinal before eventually coming unstuck 53-44.
Southby said the team was always aware there would be a series of easy games with a sudden jump in class once it reached the semifinal stage.
To prepare, Southby said they organised games against school teams and then stepped up to practise against the Silver Ferns. It served the team well.
Southby said her side took Australia by surprise and it was forced into a series of changes to gain parity. New Zealand led 30-24 at halftime.
''All their changes indicated to us they were pretty stressed. Right through the game they just didn't know what to do.''
For Southby, the win was the culmination of four years' hard work and a much sacrifice. Her girls, Grace (9) and Ella (7), and husband Roger kept the home fires burning during Southby's stints away from home.
She will hand over the under-21 reins now and concentrate on her role with the Steel. But undoubtedly, her success has elevated her in the national coaching ranks.
There are no vacancies with the Silver Ferns at the moment but Southby said once you get a taste for beating ''those Aussies'' the hunger remained.
