It comes as Newcastle ended Gold Coast's top-four hopes and reasserted their own heavyweight status with a 46-10 thrashing of the Titans - the biggest win in the Knights' NRLW history.
Made to defend their line for long periods at Cbus Super Stadium, the Broncos rolled up-field on a seven-tackle set and took an unlikely lead when fullback Hayley Maddick found prop Lenarduzzi with a short ball.
The Queensland representative barrelled over Sharks lock Brooke Anderson en route to the tryline to seal Brisbane's sixth-straight win with 16 seconds to spare in Saturday's game.
It would take a big loss to ninth-placed St George Illawarra next week and Parramatta to score similarly decisive wins in their last two games for Brisbane to miss the top four from here.
It marks quite the turnaround for Scott Prince's side, who went winless across the opening two weeks of the season.
Winger Stacey Waaka left the field just before half-time in the only blight on the Broncos' afternoon, a leg injury looking set to keep the New Zealand rugby sevens Olympic gold medallist out for the remainder of her debut NRLW season.
Stacey Waaka (l) celebrated scoring a try but later suffered a potentially season-ending injury. (Dave Hunt/AAP PHOTOS)
Earlier, the Sharks scored twice in the six minutes after half-time to erase the Broncos' four-point lead, seeking to bounce back from last week's 40-0 humbling from the Sydney Roosters.
But winger Julia Robinson grabbed a cut-out pass from Maddick to bring the Broncos back within two points, before Lenarduzzi stepped up in the dying seconds.
In Saturday's later game, Titans five-eighth Sienna Lofipo dropped the kick-off and triggered a first-half onslaught from the visitors; Newcastle's 34-0 lead at the break was the equal-largest in premiership history.
NSW second-rower Yasmin Clydsdale scythed past Lofipo for the first of her two tries on the fourth tackle of the day, before superstar fullback Tamika Upton began pulling the strings.
Shanice Parker scores for the Knights against the Titans. (Dave Hunt/AAP PHOTOS)
Upton chased down Georgia Roche's kick for her own four-pointer and an 18-0 lead after 16 minutes, before throwing the last pass in two more four-pointers in the first half.
The floodgates reopened when Ngatokotoru Arakua went to the sin bin for the hip-drop tackle that sidelined Nita Maynard with an ankle injury in the second half.
While the Knights had the personnel advantage, Upton helped right winger Sheridan Gallagher become the first Knights player to record an NRLW hat-trick.
Sheridan Gallagher (c) scored a hat-trick of tries for the Knights. (Dave Hunt/AAP PHOTOS)
The win usurps last season's 38-4 thrashing of Parramatta as the Knights' most comprehensive in four seasons.
Runners-up last year, the Titans are now unable to break into the top four with one round remaining in the regular season.
Simone Karpani joined Maynard in the Knights' casualty ward after landing awkwardly on her left ankle in the final minutes, another potential blow as Newcastle chase a third consecutive premiership.
Titans superstar Jaime Chapman also had her afternoon ended prematurely by an ankle complaint.
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