The Otago swimmer claimed silver at the world short-course championships with her time of 3min 56sec in the 400m freestyle.
She knocked 2sec off her personal best to set a New Zealand age group record, an Otago open record - which she already broke during her heat earlier - and her 200m split time of 1min 56.69sec was also a 200m national age group record.
It makes her the second-fastest New Zealand swimmer behind Lauren Boyle who holds the national 400m record of 3min 55.16sec.
Fairweather and Australian gold medallist Lani Pallister led the final in Melbourne from the start and battled for the top two spots.
Pallister pulled ahead slightly in the final few laps of the 25m pool to finish in 3min 55.04sec for gold on Tuesday night.
Fairweather was back in the pool yesterday, breaking yet another national record, this time alongside Otago’s Caitlin Deans, Ruby Heath and North Shore’s Summer Osborne in the 4x200m freestyle heat.
The team shaved 5sec off the New Zealand record to finish in 7min 50.73sec.
Fairweather led the team in style, breaking Boyle’s national open record with her swim of 1min 54.24sec. Her 100m split of 55.60sec also broke the Otago age group record.
The team got out to an early led through Fairweather and Deans followed her momentum with 1min 57.54sec to slice 1.5sec off her personal best.
But once the Australians found their flow, they were unstoppable and charged home.
Osborne (1min 59.58sec) and Heath (1min 59.37sec) carried the team home to finish fourth and qualified eighth for last night’s final at 11.30pm (NZ time).
Fairweather also competed in the 800m freestyle fastest timed final last night. She won silver again in a time of 8min 10.41sec, 0.6.34sec behind Australia's Lani Pallister who took the gold.
