The Trek-Segafredo rider crossed the Stage 3 finish with Liane Lippert (Sunweb) and Lauren Stephens (Tibco) in hot pursuit as Spratt fought bravely for 10th with spent legs.
With the stage victory, Winder claimed all 10 bonus seconds on offer and combined with the maximum bonus she savvily snatched from Spratt earlier on the stage, she now leads Lippert and the Australian champion by seven seconds before Sunday's final criterium stage in Adelaide.
"My team mate Taylor Wiles, she was leading me out perfectly," Winder said about the final kilometre. "I was just talking to her the whole time and we've been team mates for years and she's helped me with so many wins and every time I do I feel so grateful to her in the last 500 metres.
"But the entire team the whole race were really active at the front covering things, making sure I was really safe until those circuits which were pretty hard with Mitchelton just drilling it on the climbs."
Despite the final stage containing 19 seconds of time bonuses, Winder and her team should be able to ward off challengers particularly with their sprint star Lotta Henttala contesting the final win.
"I'll have to put some sprinter legs on and probably ride my Madone which is a faster Trek bicycle," Winder said surprisingly on-brand after only just finishing the race. "But we also have Lotta who's a super fast sprinter she got second on the first sprint and we'll see if we can get her on the podium again."
Spratt all-but conceded victory in our post race interview (video above).
"Of course there's always disappointment when you come here to try and win the overall but like you said, that's bike racing.
"You can't always win but I'm still really proud of the way the team has ridden."