Auckland qualified top after round-robin, losing 6-3 to Waikato but beating Counties 10-0, defending champions Hawke's Bay 7-0, Hutt Valley 4-3, North Harbour 5-2 and Wellington 10-6.
Wellington dropped three games in pool play to Hutt Valley 11-10, Auckland and Sydney Metro 5-4, with their wins coming against Counties 28-1, Hawkes Bay 2-1, North Harbour 9-0 and Waikato 11-5.
Sydney qualified top with Auckland after round-robin but were downgraded to 5th because they weren't eligible for the title.
The bulk of Cardwell's players hail from the Papatoetoe club and he said it was that unity that got them through.
"There were a couple of calls that went against us today but the girls just rolled with it, put it behind them and started again. It was great to see chins didn't drop."
Morrison pitched the entire final and finished strongly as she held Wellington's powerful lineup run-less.
"Who'd be a pitcher?" Cardwell said. "Ty was our No 1 and deserved to stay on the mound all game. We hid her from Wellington the first time we played them, keeping her fresh for this one because we thought we'd make the final."
National under-15 tournament:
Championship final: Auckland 7 Wellington 6.
Semifinals: Auckland 15 Waikato 0, Wellington 4 Hutt Valley 2