The visiting side defended 214 at Brooklands Park yesterday, dismissing the Sparks for 189.
And on Saturday, Wellington squeaked home by one wicket.
Otago, though, beat Wellington by eight runs in a crucial twenty20 fixture at the University Oval on Friday to clinch a home venue for the final this Saturday.
Unfortunately, the Sparks play Wellington and the Blaze will go into the twenty20 final with renewed confidence having won both one-dayers.
Devine skipped the opening one-dayer but returned yesterday to score 49.
Rebecca Burns scored 53 at the top and Rachel Priest reached 43 before she was run out.
Leigh Kasperek bowled a fabulous spell, taking four for 24 from 10 overs.
Fellow spinner Morna Nielsen had an off match, conceding 64 from nine overs and failing to pick up a wicket.
Otago's reply suffered an early blow with star batsman Suzie Bates undone for six.
Fellow opener Caitlin Blakely (56) and Katey Martin (45) added 83 for the third-wicket but the middle order offered precious little resistance.
Right-arm medium-pacer Allex Evans was the destroyer with four for 31.
On Saturday, Bates and Martin dragged the Sparks through to a competitive total of 196.
Bates hit 91 off 101 deliveries and Martin added 51 from 62.
he pair combined in a 75-run stand for the third-wicket but the rest of the order was unable to make much of a contribution.
Fourteen-year-old legspinner Amelia Kerr - daughter of former Wellington first-class cricketer Robbie Kerr - was outstanding with three for 29.
She accounted for both Bates and Martin and looks to be a player with a bright future.
Wellington found the chase challenging but got there with a wicket and 13 balls spare.
Priest top-scored with 49 and Burns added 42 at the top of the order.
Emma Campbell was the pick of the Otago bowlers with three for 28.
Canterbury will host Auckland in the one-day final.
