She was over 8secs clear of second-placed Kodi Campbell (2:21.40) with Briar McLeely (2:22.45) completing the Horouta trifecta.
Another Horouta paddler, Rose King, was fifth.
It was the fourth premier title for Williams, who last year won the V1 women's title at the world sprint champs in London.
Bruce Campbell and youngster Riria Atu added to Horouta's gold tally yesterday.
Campbell won the masters men's final in a national age category record of 2:05.46 — nearly 2secs ahead of Mark Malakai Williams (Manukau). Horouta's Grant Donaldson was seventh.
Atu won the intermediate girls' final, heading off clubmate Bentley Morice-Munro by 2.5secs. Horouta's Tutemakoha Kemp was fifth.
Horouta club member Vicki Flavell, paddling for Waitakere at the champs, won the masters 70 women's gold.
Campbell's son Maia collected silver in one of the finals of the day. Maia was pipped by Nga Hoe Horo paddler Elite Reti by just 0.11 of a second in the junior 16 men's decider. Horouta's Marlin Toloa was third, Kane Soto seventh and Frazor Wainohu eighth.
Horouta's Hine Brooking also narrowly missed out on gold in the junior 16 women's final. She crossed the finish line 0.64secs behind Waitangi Piripi of Nga Hoe Horo. Another Horouta paddler, Marnie Toloa, was third.
Bronze medals went to Horouta paddlers Taylynn Morete (J19 women) and Mahaki Albrett-Tureia (J19 men).
YMP celebrated another medal performance as Makauri Hape placed third in the intermediate boys' final. Mareikura's Rory Gifford was fourth.
Vesna Radonich (Hor) was fourth in the masters women's division — half a second off bronze.
Anaru Paenga-Morgan (Hor) and Keri Ngaoro (Hor) were fifth in their respective under-23 men's and women's finals.
Horouta's Mihi Aston was sixth in the golden masters women's final and Dave Langford (Hor) was seventh in the masters 70 men's final.
Yesterday was all W1 racing — 94 races in all featuring paddlers aged between 11 and 81.
Among the highlights were premier men Manutea Million (Akarana) and Kacey Ngataki (Manukau) cracking the two-minute mark in their final won by Millon in 1:57.25.
Today features W6 and W12 double-hull races.