After posting 4-147, the reigning champions defended grandly at Adelaide Oval with some clever bowling in the clutch restricting the Strikers to 8-139.
With 35 required off 27 balls, the home side would have liked its chances but the Sixers didn't panic and took 5-23 inside the next four few overs to strangle the life out of the chase.
Despite having wickets fall around her early, captain Suzie Bates (60) was holding the hosts together, at one stage scoring 37 of Adelaide's first 41 runs.
Bates then took a back seat when Tahlia McGrath (45 off 26 balls) joined her at the crease, the young Australian allrounder belting three sixes and dominating the pair's 67-run fourth-wicket stand.
But when the pair departed in quick succession, the Strikers' hopes of winning went south.
Spinner Erin Burns (2-9), player-of-the-match Dane van Niekerk (2-12) and South African seamer Marizanne Kapp (2-21) applied the clamps with the ball.
Earlier, Ash Gardner crunched 49 off 38 balls, including two sixes, and captain Ellyse Perry stroked a more sedate, run-a-ball 47 to set the Sixers up.
The pair put on 93 for the visitors' second wicket after Alyssa Healy was bowled for an aggressive 23 in the fourth over.
Legspinner Amanda Wellington (2-19 off four overs) and Kiwi allrounder Sophie Devine (2-25) impressed with the ball in a gallant losing cause.