Nancy Harman led Southern Vipers to a narrow three-wicket win over Thunder to make it three wins in a row for the defending champions.
All-rounder Harman, making her first appearance of the season, came to the crease with Vipers wobbling at 136 for 6 and needing 207 - and behind the DLS with rain falling. But she beat her previous best of 23 not out to guide her side to victory and keep Vipers unbeaten against Thunder.
Earlier, England A batsman Seren Smale surpassed her previous best of 94 - against Central Sparks last season - and scored her third career Rachael Heyhoe Flint Trophy fifty, but was heartbroken to be run out on 99.
Vipers elected to bowl first and restricted Thunder to 16 runs in their opening 10-over powerplay, with Shachi Pai bowled by Linsey Smith.
But Smale and Katie Mack got the innings going with a risk-free approach of singles and only eight boundaries in their 94-run stand. The partnership underpinned the innings, albeit at a slow pace, as Smale reached her half-century off 84 balls.
She earned life on 53 and 65 - a caught and bowled by Smith and a drop at deep midwicket - but showed great skill to pepper her innings with six fours, all in the V.
Mack and Fi Morris fell within two balls of each other with the score on 111. The Australian was involved in a classic run-out mix-up before Morris skied a pull to give Alice Monaghan the Vipers' first wicket of the season.
Ellie Threlkeld was bowled trying to ramp Mary Taylor and Naomi Dattani drove straight back to Charli Knott, but Danni Collins joined Smale to give the innings some life at the back end.
All eyes were on Smale to get to three figures for the first time in her career. She had to contend with a lack of batting and wickets falling at the other end.
Collins - after making 41 off 21 balls - and Tara Norris fell to Smith in successive balls. The left-arm spinner finished with 3 for 19, the most economical spell by a Vipers bowler for the second week running.
Phoebe Graham was bowled by Taylor with Smale needing five runs from the last two overs. But she faced just four balls before she was run out attempting to reach the milestone, and she remained sprawled in the diving position for a while before dragging herself away.
Vipers' reply got off to a stuttering start when Norris hooked an in-swinger to bowl Ella McCaughan with the fifth ball of the innings before Knott ended her run of 41, 58 not out and 40 when she hit short midwicket.
In the rain, Vipers tried to chase down DLS's target, with Georgia Adams hitting a series of straight boundaries with aplomb. But Abi Norgrove came forward and was caught behind to make it 46 for 3 as DLS rocketed from 52 to 70.
Adams and Georgia Elwiss put Vipers comfortably ahead with a partnership that oozed quality before Elwiss was strangled down the leg side and Emily Windsor was lbw to Graham.
Adams reached her 50 off 62 balls - her 15th half-century - but top-edged Dattani to bring the visitors back into the game. Rhianna Southby, Harman and Monaghan then scored the final 72 runs to see Vipers home with 39 balls to spare.