The Rebelettes ran out 2-16 to 4-7 winners against Armagh, who were edged out of the semi-final placings.
Holders Cork now face Dublin next weekend, with fourth-placed Kerry taking on runaway table-toppers Mayo.
Kerry made it through as a result of their superior scoring difference over Armagh, as five teams finished locked on 12 points each after the group stages concluded, nine behind pacesetters Mayo.
Cork got off to the perfect start as captain Ciara O’Sullivan netted after just 30 seconds after Orlagh Farmer’s effort struck the crossbar.
Cork were 1-5 to 0-0 clear before Aimee Mackin got Armagh’s opening score and the Orchard County were given another significant boost when midfield inspiration Caroline O’Hanlon netted.
Later in the first-half, Armagh missed a glorious chance for a second goal when Aimee Mackin screwed a penalty off the post and wide and missed chances were punished at the other end when Cork’s dual star Briege Corkery pointed to establish a 1-9 to 1-2 lead.
Mackin made up for her missed penalty by netting Armagh’s second goal but Armagh still had plenty of work to do at half-time, trailing by 2-3 to 1-11. Cork seemed to have put the result beyond doubt with their second goal shortly after the break, O’Sullivan on target again, but Armagh rallied with goals from Fionnuala McKenna and Mackin to make a game of it.
But Cork held on for the vital win and can now begin preparations for another big showdown with Dublin next weekend.
In Division 2, Sligo maintained their second tier status by seeing off Meath in a relegation playoff. The Westerners ran out 2-14 to 2-12 winners, condemning Meath to Division 3 football in 2017.
Sligo scored two late points to get over the line, after they had trailed by three points at half-time.
Elsewhere, the Division 3 League final will be contested by Munster rivals Waterford and Tipperary, who scored semi-final wins over Leitrim and Wexford, respectively.
Waterford ran out comfortable 7-15 to 0-6 winners over Leitrim while Tipp had a much trickier assignment against Wexford, before winning 5-11 to 4-7.
In Division 4, Antrim and Limerick will contest the showpiece decider. Antrim beat Longford 2-11 to 0-13 in their semi-final, as Limerick saw off Wicklow, 0-14 to 2-6.