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The Dunedin swimmer will be the youngest of the 4000 competitors at next month's Youth Olympics.
Fairweather's birthday of December 31, 2003, is the cut-off date for entrants, but leaves her one day too old to enter the 2022 Games.
As a result, she will battle it out with athletes who may have turned 18 on January 1 this year.
It is a big ask for a 14-year-old.
But it is not something that is fazing her too much. Indeed she has already proved she can foot it with those much older than her.
``I guess it is a little bit [intimidating], but it's also pretty cool,'' she said.
``They're older, they're all probably more experienced, it'll be cool to learn off them.''
The year 10 Kavanagh College pupil got her first taste of major international competition at last month's Junior Pan Pacific Championships in Fiji.
There she raced the best from powerhouses Australia and the United States while being in a similar position of competing against older competitors.
She was happy with how she went, swimming personal-bests and claiming an impressive fourth in the 400m freestyle.
It was the latest experience of what has been an achievement-filled year.
She claimed three silver medals at the national open championships and now holds 12 national age-grade records.
In the 14-year-old age-group, she owns the 100m, 200m and 400m girls freestyle records.
She will get the chance to break those again in Argentina, alongside the 800m one, which she is just over 0.05sec off.
Around all that, she will also fit in racing in the mixed freestyle relay.
Despite the frequency with which she does it, breaking records is not a huge focus.
``I guess it depends on how close I am to them. If I am close to them, I guess it is a target.
``But I just race and see what happens most of the time.''
It is a tactic that is clearly working and showed through in her selection for Buenos Aires - New Zealand swimming was given only two girls and two boys spots.
She will leave Dunedin on September 30 and spend three weeks in Argentina. The swimming will be held in the middle week.
That gives her the chance to acclimatise and train in the lead-up, while also getting to see some other sports and have a look around the city.
As for the swimming, her ultimate goal is to make a final.
While she knows there will be plenty of fast swimmers there, she said it would be awesome to race them and that competition helped push her along.