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The 18-year-old has been named in the national side for the twenty20 series against the West Indies next month.
Auckland batsman Lauren Down is also in line for a debut, with the 22-year-old named in the ODI squad.
Heffernan is a talented left-arm seam bowler who forced her way into the squad with some frugal bowling for the Sparks during the domestic season.
But she is also a very promising midcourter with a bright future in netball. She is a training partner with the Steel and was a New Zealand secondary schools squad member last year.
At some stage she will have to choose between the codes, but not yet.
''I'm happy doing both and I'm not going to make a choice until I really have to,'' she said.
Heffernan said the Steel was supportive of her cricket ambitions and she would miss only two weeks while with the White Ferns. If she had to pick, she would be torn, but her promotion to the national side is a huge incentive.
''It was something I didn't expect. If it was going to happen I thought it might be in a couple of years when I'd played more cricket.
''But they are both still very even. They are hard to compare because they are both so different and they are both equal at the moment.''
Heffernan shot to fame last season when she took four wickets in the twenty20 final to help Otago shock Canterbury.
She will be joined in the White Ferns by Otago team-mates Suzie Bates, Katey Martin and Leigh Kasperek.
White Ferns coach Haidee Tiffen said it was Heffernan and Downs' raw talent which saw them gain selection.
''Both Kate and Lauren are impressive athletes in their own right and will definitely bring that dynamic edge that we're looking for,'' Tiffen said.
''The fact that Kate is a left-armer was certainly a factor in her selection, as she will bring that point of difference.
''We see an immense amount of potential in Kate, particularly as we look ahead a bit further to a World Cup in New Zealand in 2021.
''Lauren's been on our radar for a while in both formats and we also think she's one for the future. She's explosive with the bat and is a terrific fielder across the park.''
Canterbury all-rounder Kate Ebrahim (nee Broadmore) returns to the ODI squad, while Northern Districts opener Natalie Dodd and pace bowler Haley Jensen also return to the international scene in the T20 squad.
Bates will captain both sides, which feature the familiar faces of vice-captain Amy Satterthwaite, hard-hitting all-rounder Sophie Devine and 17-year-old leg-spinner Amelia Kerr.
Experienced Auckland batsman Katie Perkins has missed selection after having limited opportunities following a broken thumb in December, while leg-spinner Erin Bermingham was unavailable.