She also set a new Northland Open long course record in all five of her events. As well as breaking her own 50m record, she claimed the 100m and 200m records that were set by Northwave's Ashley Masters in 2008.
She took seven seconds off the time she set last March for the 16-17-year 400m individual medley and went a second under the 200m IM open record set by the Bay of Islands' Carla Marsh in 2011.
Meanwhile Bay of Islands swimmer Emilia Finer shed over 15 seconds off the 800m freestyle record, ousting Northwave's Ellie Eastwood who set the mark in 2013.
Finer, 13, also set a new record in the 12-13 girls 200m butterfly and made four finals in her eight events. Her best finishes were in the 200m butterfly and 800m freestyle where she ended fourth.
Bream Bay's Paul Linton went under the 100m backstroke time set by Matthew Gordon three years ago.
Meanwhile Smith's Northwave compatriot Annabelle Simpson, 17, medalled in all three of her backstroke events, winning silver in 100m and 200m and bronze in 50m.
She took out the 17-year age group long course record for 50m backstroke set in 2000 by Kamo's Kushla Chapman and set new Northland Open long course records in all three strokes, two of them her own records and one set by clubmate Hayley McIntosh in 200m backstroke in 2016.
Smith and Simpson were selected into the New Zealand team to compete at the Oceania Championships in Papua New Guinea in late June, and their coach, Monica Cooper, was selected as one of the coaching staff, but they had to withdraw.
Both girls are on the long list to go to the Youth Olympics in Argentina in October and the qualifying event for that is NZ Opens which is the first week of July.
Young Northwave swimmer Tyler Jepsen, 13, made his mark on the competition, taking silver in 200m backstroke and in 400m freestyle while setting a new time for the Northland long course age group record, set by Bay of Islands' Jeremy Elliot in 2015.
Jepson placed fifth in 400m freestyle and eighth in both the 100m backstroke and 200m freestyle.
Fourteen-year-olds Nellie Clark and Madeline Whittam also managed top-10 placings in their breaststroke events at the championships.
Clark was fifth in the 100m while Whittam was fifth in the 200m, seventh in the 50m and eighth in the 100m.