Hawthorn's finals hopes are on thin ice after their forward Aine McDonagh missed a snap with just 18 seconds remaining as GWS pulled off an upset one-point win at Sydney's Henson Park.
And at Windy Hill on Sunday, Chloe Molloy and Cynthia Hamilton unleashed an early goal barrage to lead Sydney to a 51-point victory over Collingwood.
Hawthorn (5-5) slipped to ninth with just two rounds remaining after falling 7.13 (55) to 7.12 (54) to the 15th-placed Giants (2-8).
The Hawks trailed by eight points with two minutes remaining before Jacqueline Dupuy took the ball out of the ruck and snapped truly to make it a two-point game.
Then with just 25 seconds remaining, McDonagh took a mark in the pocket, giving her the chance to win the game.
McDonagh played on but sent her snap wide, allowing GWS to hang on for a rare victory in what marked the perfect way to celebrate Tilly Lucy-Rodd's 100-game milestone.
"It was crazy. It was really stressful out there," Lucy-Rodd told Fox Sports.
Lucy-Rodd finished with a game-high 25 disposals against her former club, while Alyce Parker kicked three goals to spearhead the Giants' shock win.
At Windy Hill, Molloy and Hamilton had three goals apiece by the opening minute of the second term against Collingwood before forward-turned-ruck Taylor Smith chipped in with three of her own as Sydney cruised to the 12.8 (80) to 4.5 (29) victory.
The result kept seventh-placed Sydney (7-3) in the hunt for a home final with two rounds remaining.
Collingwood (1-9) are still in danger of finishing with the wooden spoon.
Hamilton finished with 3.1 and one goal assist from 14 disposals, while former Collingwood star Molloy tallied 3.1 and five marks alongside 15 possessions.
Smith, a key forward who won two flags with Brisbane before moving to Sydney at the end of last year, has been thrust into the No.1 ruck role since Ally Morphett went down with an ACL tear earlier this month.
The 26-year-old has thrived in the lead role, tallying 20 hitouts, six marks, 12 disposals and three goals against Collingwood.
"I honestly love it," Smith told Channel 7 when asked about her full-time move to the ruck.
"It was really funny, because everyone was like, 'Wow, I didn't know you could jump that high'.
"And I was like, 'I was a high jumper up until I played footy', and they're like, 'Well thank god - we didn't get you for that, but we'll take it'."
Magpies star Brianna Davey suffered a huge scare in the first quarter when she rolled her right ankle while attempting to twist out of a tackle, but she was able to return to the field.