The robbers, armed with a knife and a club, struck the home of the 17-year-old girl’s mother in the country town of Bundanoon on Thursday, police say.
Her mother told the men her daughter no longer lived there.
It is not clear how the robbers found the family address. The Facebook image was at the grandmother’s Sydney house.
The men searched the house and took a small amount of cash and a small number of personal objects before leaving.
No-one was injured.
The girl had earlier posted a picture on her Facebook page of a “large sum of cash” she had helped count at her 72-year-old grandmother’s home in Sydney, 120 km (75 miles) north-east of Bundanoon.
Following the incident, police have issued a warning over the dangers of posting sensitive information online.
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