The 16-year-old left her home on Eyre Street in Ballarat on November 22, 1973, to meet a friend at the bus stop, but failed to show up.
She didn't attend work at Ballarat Woollen Mills, nor did she collect her wages or holiday pay.
Police on Friday released a new computer-generated image of what Sherrlynn could look like in 2022, in the hope someone recognises her.
"Police have exhausted all known avenues of inquiry after Sherrlynn's disappearance almost 50 years ago," Ballarat Detective Acting Sergeant Andrew Barnes said.
"However, we are determined to find out what happened to her so we can end the trauma for her family and loved ones."
He said there was nothing to indicate her disappearance was suspicious, but police want to speak to anymore who might know her movements over the years.
"Sherrlynn, if you are out there - it is not a crime to disappear and police will not disclose your whereabouts to anyone if that is your wish - we just want to know that you are safe," he said.
Sherrlynn's friends and family have spent five decades wondering what happened to her.
Sadly, her mother died in 2016 and her two brothers are the only remaining family members.
There were hopes that a body found in the United States seven years after her disappearance was her, however DNA testing in 2010 revealed it was someone else.
Detectives have followed up a number of possible DNA matches in Australia, but none have been found.
At the time of her disappearance, Sherrlynn was described as 165cm tall with a medium build, red hair, hazel eyes and a fair complexion.
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