A patient 17-run, eight over partnership between tail-enders Katelyn Pope and Alex Price saw the Scorpions hold on for 48 overs, despite losing 4/6 earlier.
A clump of wickets between the 33rd and 38th overs quickly derailed the Scorpions batting innings, with stand-in skipper Tegan McPharlin toiling hard to top-score for her side with 37 runs.
Earlier in the day, Tasmania captain Brooke Hepburn won the toss and elected to bowl, with Bridget Patterson (18) and Tabatha Saville (21) opening South Australia’s innings.
The pair kept the run rate slow and steady, putting on 39 runs for an almost 15-over opening stand.
A 59-run partnership between McPharlin and Tahlia McGrath appeared to be steadying the ship, however the loss of McGrath at 3/112 sparked a collapse, with just another 45 runs added further to the teams's total.
In reply to the Scorpions 157, half-centuries to Georgia Redmayne (56) and Corinne Hall (55 not out) were exactly what Tasmania needed to see them to 4/158 in under 40 overs.
Tight bowling from McGrath was the highlight for the Scorpions, with the seamer taking 1/15 from 10 overs.
Pope (1/21) and Amanda-Jade Wellington (1/34) were the only other bowlers to take a wicket, plus a quick runout from Saville to dismiss Meg Phillips in the sixth over.