"Maybe if it was 10 laps it may have spat them out. I guess you have to be pretty proud after the silver medals on the track and now this but you always want to do better."
Williamson said she had just two days off her bike following the track world championships before some long training rides, a road race in Timaru and a kermesse victory in Europe.
"At first, the race was only 65kms and so I didn't feel I needed to go out and smash it in training on the longer stuff. But they changed it to 80kms just before the championships."
The BikeNZ rider was handy to the lead throughout the race, keeping out of the way of a number of crashes. The Great Britain squad produced the major lead-out train, promoting their sprinter Lucy Garner to the win ahead of Norway's Eline Brustad in 2:11.26.
Williamson fought hard at the finish sprint to be half a wheel from Italy's Zita Stricker for the bronze.
It completes an outstanding junior career for Williamson who has her sights set on racing for a road team in Europe or the US next year.
The under-23 men (Tom David, Josh Atkins, and Tom Scully) race over 177kms tonight (NZT) and the elite women (Linda Villumsen, Emily Collins, Emma Crum, Kate Chilcott) also tackle 145km. The elite men race on Monday (NZT).
Results, junior women, 80kms: Lucy Garner (GBR) 2:11.26, 1; Eline Brustad (NOR) same time, 2; Anna Zita Stricker (ITA) st, 3, Sophie Williamson (NZL) st, 4.