Harris compiled a season-high score of 73 and then took 4/33, clearing out Northern Districts’ tail to secure her team’s second title for the 2017-18 season.
It is the third time West Torrens has won the women’s first-grade competition (previously 2008-09 and 2012-13) and the first time they have become champions in both the one-day and Twenty20 formats.
West Torrens captain Jess Joseph won the toss and elected to bat first at SACA’s brand new Karen Rolton Oval.
Opener Kayla McGrath (5) fell cheaply, however Tahlia McGrath (45) and Angela Treloar (25) combined to put on a 63-run partnership before Treloar was bowled by Neisha Iles (1/31).
Youngster Darcie Brown (2/23) took two of the most important West Torrens scalps in Tahlia McGrath (45) and veteran Lauren Ebsary (0) on consecutive balls.
Harris then took control and built partnerships with Ellie Falconer and Caroline Ward as West Torrens set a competitive total of 204 from its 50 overs.
Eagle Falconer (3/18) was dangerous with the ball, dismantling the Jets’ top order by dismissing Tegan McPharlin (1), Britt Perry (0) and Tabatha Saville (8).
Samantha Betts gave the Jets a fighting chance, putting on 63 runs from just 55 balls, with Katie Rowe’s patient 23-run knock also contributing.
Harris took away any chance of Betts finding a stable batting partner, however, removing batters seven through 10, with the final three wickets falling for just one run.
The Jets lasted 42 overs but made just 161, 44 runs short of victory.