Fairweather put in a fine effort in the women's 400m freestyle final, finishing a close second behind former Dunedin swimmer Carina Doyle.
Doyle clocked a winning time of 4min 16.40sec, with Fairweather finishing strongly to record 4min 16.89sec.
It was a personal best for Fairweather, whose time was 8sec quicker than she tallied in the heat.
It was almost 6sec better than her previous personal best and qualified her for the Junior Pan Pacific Championships and Youth Olympic Games.
It was also a 14-years national age record, her second of the meet.
She had also set a record in the 800m freestyle earlier in the week.