The 29-year old West Australian put in two consistent runs, moving from eighth to fifth after improving her time by nearly three tenths of a second on her second run.
Her team-mate, Michelle Steele, 26, also performed solidly, making a similar improvement on her second run to maintain her ninth place.
The two Australians were separated by just 0.09 of a second after the first run, with Chaffer just in front in eighth place.
They made similar improvements on their second run down the 1507 metre track, with Chaffer climbing more places as some of the more fancied sliders made errors and dropped back.
“I was happy with the day and felt like I drove closer to where I know I can,” Chaffer said.
“I had two solid runs and it’s a great way to go into the Christmas break.”
Steele was pleased to continue her return to form after a 12 month break away from the sport.
“I was happy to finish in the top 10 with this being my first time at this track,” she said.
“I’m now looking forward to a short Christmas break, before the World Cup resumes in January.”
After five rounds of the FIBT Skeleton World Cup, Chaffer and Steele are ninth and 10th respectively in the overall standings.
Held at the venue of the 1992 Olympic Winter Games, the La Plagne track is situated high in the French Alps.
American, Katie Uhlaender, won the event by the convincing margin of 0.49 of a second, ahead of Sarah Reid (Canada) and Marion Thees (Germany) who finished in a dead-heat for second place.