The Blaze 137 for 1 (Kelly 55*, Knott 54*) beat Essex 136 for 9 (Heap 46, Higham 3-24) by nine wickets
Charli Knott starred with bat and ball as The Blaze cruised past Essex at Chelmsford with 4.1 overs unused to remain in contetion at the top of the Vitality Blast table.
The Australian allrounder took 2 for 24, teaming up with fellow spin duo Lucy Higham and Maria Andrews to restrict the home side to 136 for 9.
Knott then contributed an unbeaten 54 from 35, sharing an unbroken partnership of 95 from 64 with captain Marie Kelly, who posted 55 not out from 44 - her first half-century of the tournament.
Essex batter Liberty Heap continued her recent renaissance, equalling her career-best T20 performance with 46 from 31, but it was not enough to deny The Blaze a third consecutive win.
Put in to bat, Essex were soon in trouble as the visiting spinners established control and captured three wickets inside the first four overs, including those of experienced pair Lissy Macleod and Jo Gardner.
Heap and Anneke Bosch led a mini-recovery, with the South African's powerful strokeplay yielding a string of boundaries until she was trapped in front by a slower delivery from Georgia Elwiss.
But Heap continued to build momentum, cutting and cover-driving fours off Knott and using her feet against Higham to clear the ropes, moving within one stroke of what would have been a maiden T20 half-century.
The offspinner tempted Heap again next ball and this time she holed out to long-on, to be followed in similar fashion by debutant Amelie Bishop and Ariana Dowse as the home side stumbled towards the end of their innings.
Two wickets from successive deliveries stifled Essex during the final over, including Knott's smart fielding to run out Sophie Munro at the non-striker's end and left The Blaze to chase a modest 137.
Essex's prospects of defending that were hampered further by a couple of early misfields in the deep and the openers took advantage, with Tammy Beaumont thumping back-to-back fours off Eva Gray.
Kelly also gathered pace following a slow start and the pair had trimmed off almost a third of the target by the time Esmae MacGregor came on to pierce Beaumont's defences with a swinging yorker.
Knott maintained The Blaze's impetus, crashing Gray and Kate Coppack to the off-side rope and then slamming MacGregor for successive fours before hoisting Bosch over midwicket for a maximum.
The skipper was first to pass 50 from 42 balls, drilling Bosch to the cover fence, with her partner faster to the landmark by eight deliveries before punching Munro for another boundary to seal victory.
