The Sparks, who had been ahead in their quest to chase 169, had just lost four wickets for seven runs, handing the momentum back to the Hearts.
But Gray delivered, smacking 35 off 13 balls to see the Sparks home for a four-wicket win at University Oval yesterday afternoon.
Anna Browning (19 off 12) added control to their partnership of 55 off 23 to finish the game.
It was a solid performance from the Sparks — their first victory since Alexandra — and showed grit when they were under attack from the Hearts.
The Sparks were on top for much of the chase, but the Hearts strangled them through the middle to stunt their flow.
PJ Watkins, opening in place of sidelined Bella James, brought up her maiden Super Smash half century off 34 balls.
Felicity Robertson went early when she skimmed her shot high.
Watkins started striking the ball well, crushing four boundaries off Bree Illing’s over.
Watkins and Caitlin Blakely formed a nice partnership through the power play, creating good momentum to have the home side in front.
Watkins slapped another boundary to bring up a 50-run partnership with Blakely off 28 balls.
Josie Penfold — who finished four for 29 — bowled Blakely for 26, making the Sparks 71 for two.
Watkins kept the Sparks ahead, picking the right areas of the field to attack, and brought up her half century.
Laura Harris, who will never die wondering with the bat, was removed for 15 and put the Sparks 107 for three in the 13th over.
Watkins went the next over, Inglis went for five in a brilliant catch from Lauren Down and Olivia Gain perished for a duck.
The Sparks then found themselves 114 for six. But Gray and Browning took control to finish 169 for six.
Earlier, Izzy Gaze signalled her intent with several boundaries.
Prue Catton lasted three balls before she skied a shot to Harris for a comfortable catch.
Gaze used the quick outfield to her advantage as she continued to find the ropes.
Captain Maddy Green met a similar fate to Catton, ending in an easy catch for Robertson.
Gaze brought up her maiden half century off 37 balls.
Sparks seamer Louisa Kotkamp had been one of the home side’s best with the ball. She made the all-important breakthrough, removing Gaze to put the Hearts 66 for three.
Harris kept the Hearts batters on their toes when she bowled her first Super Smash over, conceding just two runs.
Strike bowler Emma Black was brought back into the attack to break up the partnership of Brooke Halliday and Down. She struck immediately when she teamed with Kotkamp to run out Down.
Bella Armstrong holed out to Blakely at long on, leaving the Hearts 105 for five in the 16th over.
The final overs belonged to the Hearts as they ramped up and started to take the game away.
Halliday whipped a six through the offside and brought up 50 off 40 balls.
Josie Penfold finished the penultimate over with a mammoth six to get the Hearts to 151 and hand the visitors a bonus point.
The Hearts finished 168 for five.
HEARTS
I Gaze b Kotkamp 52 (40)
P Catton c Harris b Black 4 (3)
M Green c Robertson b Kotkamp 1 (13)
B Halliday not out 58 (43)
L Down run out 15 (17)
B Armstrong c Blakeley b Deerness 7 (3)
J Penfold not out 23 (11)
Extras (1lb, 7w) 8
Total (for 5wkts, 20 overs) 168
Fall: 1-19, 2-43, 3-66, 4-95, 5-105.
Bowling: PJ Watkins 2-0-16-0, E Black 4-0-46-1 (2w), L Kotkamp 4-0-22-2 (2w), E Gray 3-0-29-0, C Deerness 2-0-25-1 (2w), A Browning 1-0-9-0, L Harris 2-0-12-0, F Robertson 1-0-8-0.
SPARKS
F Robertson c J Penfold b M Penfold 9 (12)
PJ Watkins c Green b Armstrong 50 (36)
C Blakely b J Penfold 26 (17)
L Harris c Halliday b J Penfold 15 (12)
P Inglis c Down b J Penfold 5 (7)
A Browning not out 19 (12)
O Gain c P Catton b J Penfold 0 (1)
E Gray not out 35 (13)
Extras (3lb, 7w) 10
Total (for 6wkts, 18.2 overs) 169
Fall: 1-14, 2-71, 3-107, 4-107, 5-113, 6-114
Bowling: A Hucker 2.2-0-25-0 (2w), B Illing 4-0-37-0 (1w), M Penfold 3-0-29-1 (1w), B Armstrong 3-0-26-1, B Halliday 2-0-20-0, J Penfold 4-0-29-4 (3w).
Result: Sparks won by four wickets.
