Northern Diamonds 160 for 5 (Winfield-Hill 51, Villiers 3-42) beat Sunrisers 157 (Grewcock 50, Levick 3-23) by five wickets
The Diamonds opener passed 50 for the eighth time in her last 10 innings in the tournament to ensure the defending champions - defeated by Central Sparks on Saturday - responded with a comprehensive win at Chelmsford.
Winfield-Hill then top-scored with 51 from 43 balls and Bess Heath struck an unbeaten 32 from 25, as the visitors chased down their target with 21.3 overs to spare.
Scott and Woolston, opening the attack after Diamonds had lost the toss and surprisingly been invited to bowl in overcast conditions, established control as they made the ball swing from the start. Woolston brought one back to uproot Cordelia Griffith's off stump in her second over and then found movement in the opposite direction to clip the bails and pick up the prize scalp of Grace Scrivens for 11.
Mady Villiers departed for a second-ball duck, clipping Scott to the diving Katherine Fraser at midwicket and, when Saskia Horley's pull off Abi Glen flew straight to Hollie Armitage, Sunrisers were deep in the mire at 32 for 4.
Grewcock and Jo Gardner dug in for a concerted rebuilding campaign during the middle overs, clawing their way back into the game with a spirited fifth-wicket partnership of 65. Gardner had just begun to open up, drilling Fraser back past the stumps for an isolated boundary, when she miscalculated a Chloe Tryon delivery and was bowled for 32 - after which Sunrisers' innings hit the buffers again.
Teenage left-hander Grewcock, having battled hard to complete her half-century from 91 balls, was then caught behind off the 93rd - the first of two wickets in three deliveries for Levick.
Kate Coppack's breezy unbeaten 16 at least hauled Sunrisers above the 150 mark before they were bowled out with four overs unused - but the total never looked like one they could defend with any degree of confidence.
Winfield-Hill immediately set the tone for Diamonds' response, slamming Coppack to the midwicket boundary twice inside the opening over as she and Sterre Kalis built a belligerent partnership of 53. Coppack's luck seemed to be out, with Kalis edging her just over the stumps for four, and it was Sunrisers skipper Kelly Castle who eventually achieved the breakthrough, trapping the opener in front with a slower delivery.
With Winfield-Hill striking the ball confidently and Armitage in no mood for caution, as she cracked Abtaha Maqsood to the rope three times in her first over, Diamonds appeared to be coasting towards their target.
They were held up by Villiers, whose wily offbreaks brought her figures of 3 for 42 - the trio of victims including Winfield-Hill and Armitage, who until then had been highly effective against the slower bowlers in her knock of 30 from 32. However, Heath clubbed Villiers over long-on for the first six of the match - and then flayed the second off Eva Gray to seal Diamonds' victory in style.