Queenslander Harris was the unquestioned star for the London Spirit in the first week of the competition, with her two brilliant half-centuries and nerveless death-over helping the champions to a table-topping three wins.
But the hitherto winless Rockets, under Gardner's leadership, spoilt the hosts' 100 percent record with a comprehensive 33-run win at the Spirit's Lord's home on Thursday, with all three of the Nottingham-based side's Aussies providing significant contributions.
Gardner herself, who's looked in good nick with the bat during her side's initial struggles, joined forces with Ashes rival Nat Sciver-Brunt for a fine 60 partnership for the fourth wicket that helped, along with Bryony Smith's 42, to propel the Rockets to 6-149.
Gardner clouted 25 off 22 balls, with a couple of fours and a six, while Sciver-Brunt, perhaps the best player in the league's brief history, added another half-century to finish on 51 not out off 29 balls.
Spirit's assault on the total was quickly scuppered as Gardner (2-14 off 15 balls) got rid of her struggling compatriot Georgia Redmayne (nine off 15) before Australian international Heather Graham (2-28 off 20 balls) grabbed the key wickets of Cordelia Griffith and Issy Wong.
Aussie legspinner Alana King also chipped in with 1-30 but the principal destroyer proved to be England left-arm spinner Kirstie Gordon (4-15), who induced Harris to slog into the hands of deep square leg for just eight off seven balls.
It was Harris's first proper flop with the bat after innings of 89no, 18 and 50no, although she's still second in the list of leading run-scorers on 165 runs, 12 behind her illustrious compatriot Meg Lanning, while scoring at a league-high strike rate of 173.68.
Another Australian international Charli Knott did her best to try to drag Spirit back into the contest with her suitably spirited 33 off 25 balls but to no avail as they were skittled out for 116 off 95 balls.
