South East Stars were 76-3 at Moseley CC in Shirley after being put in by Central Sparks before Chathli – who scored her third 50 in four innings – and Davidson-Richards shared 127 for the fourth wicket.
Davidson-Richards’ 68-ball knock included two sixes and five fours, while Chathli hit nine boundaries and remained at the crease until the 47th over, despite Katie George’s 4-26, before Stars were finally all out for 270.
Youngster Tilly Corteen-Coleman then removed the Sparks openers but Davina Perrin made a sparkling 50 off 51 balls.
When she was caught off Dani Gregory, Chloe Brewer (54) and Bethan Ellis (57) added 103 for the sixth wicket, but both fell to Alexa Stonehouse (3-26) and Sparks could only reach 250-9, leaving the Stars on the brink of qualification.
At Radlett, Sunrisers reduced Western Storm to 84-6 after winning the toss and opting to field first.
Sophie Munro claimed 3-42 but an unbeaten 45 off 42 balls by Amanda-Jane Wellington enabled the Storm to reach 180 all out.
Sunrisers looked on course for their seventh win when Cordelia Griffith (39) and Lissy Macleod (48) were together, only to lose their last six wickets in the space of nine overs for just 20 runs, all out for 150 with Chloe Skelton taking 5-29.
