Tyra Ekepati had played 13 NRLW matches for St George Illawarra before making her Fetu Samoa debut this year. The 19-year-old centre has since scored three tries.
Fetu Samoa's 24-6 victory over England in Wollongong secured their first World Cup semi-final berth, against the Kiwi Ferns next Saturday in Newcastle.
It is Samoa's third attempt at the tournament and their first qualification since 2008, following earlier campaigns in 2003 and 2008.
Eight players in the 17-member squad are 22 or younger, including six aged 20 or below. Eighteen-year-old Freedom Crichton Ropati scored a hat-trick against England, while 20-year-old Mercedez Taulelei-Siala has three tries across wins over Wales and England.
Co-captain Annetta Nuuausala, 31, said the younger players brought maturity and helped build connections on and off the field.
"They keep us on the toes and are always willing to learn."
Nuuausala said the new players would not be intimidated by New Zealand: "They love the pressure - they see that as a privilege."
Halfback Pauline Piliae-Rasabale, 33, and Nuuausala are among six players who featured in the 2025 Pacific Championships, when Samoa lost 22-20 to the Ferns.
Piliae-Rasabale said the team wanted its younger players to enjoy their success, while being ready to perform regardless of the opposition.
Ekepati said the support from family and community meant a great deal: "It's not common girls get that support but it's in the blood, the culture, the families and they've kept turning up for us."