After winning the toss and batting first on Sunday in warm conditions, Sixers skipper Ellyse Perry proved to be the difference between the two sides.
Perry thumped an unbeaten 80 off 54 deliveries to take her season aggregate to a league-record 617, moving past the previous benchmark held by Lanning, who compiled 560 runs in 2015/16.
The Sixers, after posting 2-183, dismissed the Scorchers for 151, meaning plenty rides on the Scorchers final two games of the season with a finals berth on the line.
Perry backed up her knock with bowling figures of 2-21, capturing Scorchers opener Amy Jones in her first over before removing Heather Graham.
Lanning (76 off 51 balls) was heroic in the Scorchers' run chase but, aside from a cameo from Mathilda Carmichael (19), there wasn't enough help.
"Ideally, if we could have gone (restricted the Sixers to) 160 or under, that would have been a good effort but they got off to a flyer and had wickets in hand towards the end which always makes it difficult," Lanning said.
"We tried our best - it just wasn't to be."
The Scorchers travel to Alice Springs on Friday for two must win games against the Adelaide Strikers next weekend.