The teenager and her mother were travelling along Blackgate Road at Freshwater Creek around 11.15pm when the accident occurred.
Speaking to the Geelong Advertiser, Torquay captain Phillip Campbell said the pair were coming over the hill when they hit the cow and probably wouldn't have seen it because it was black.
"It was one of those freak accidents and the pair had a very lucky escape," he said.
The 17-year-old spent a night under observation at the Geelong Hospital before being released yesterday.
More details in the Geelong Advertiser.