The sides then traded tries, with the Ferns scoring through Honey Hireme-Smiler and Samoa through Ricshay Lemanu, before Stephens-Daly's impressive solo run extended the gap to 12 points at halftime.
While the Ferns were having the better of the play, the wet conditions in Auckland made things difficult and both sides had their handling woes.
It didn't get much better in the second half in that aspect, with both sides seeing promising attacks fizzle out after a dropped ball.
The Ferns were able to strike three times in the second period, through Stephens-Daly, Katelyn Vaha'akolo and Crystal Tamarua, pushing the scoreline out to a comfortable margin. And while Samoa crossed again through Leianne Tufuga, they were unable to keep touch with New Zealand.
Both sides finished the match with just a 65 per cent completion rate, with the Ferns making 14 errors to Samoa's 13, while Samoa missed 37 tackles to the Ferns' 16.
Speaking after the match, Kiwi Ferns lock Charlotte Scanlan said it was a good showing from a team who were yet to spend much time as a group, and was thankful to be in a position to play an international match this year.
"The culture within the team is really growing," Scanlan said. "Chucking a bunch of girls together into one team, you never really know what's going to happen, but we really gelled.
"To be the only country that gets to do it, it's an honour and we're so thankful to be from a country like New Zealand."
Kiwi Ferns 28 (Autumn-Rain Stephens-Daly 2, Karli Hansen, Honey Hireme-Smiler, Katelyn Vaha'akolo, Crystal Tamarua tries; Hansen 2 cons)
Fetu Samoa 8 (Ricshay Lemanu, Leianne Tufuga tries)
HT: 16-4