The 22-year-old is currently sharing a cell with around 250 other women in one of the most notorious prisons in Colombia but is maintaining her innocence, saying she was set up by a man she'd only just met.
Cassandra's family told 9NEWS that the man gave her a package, saying it contained the headphones she had bought for her family and friends.
"(He told her) if you bulk buy these gifts I can get them cheaper," sister, Kayla Sainsbury, said.
"It came to her already packaged and concealed and she put it straight in her suitcase. She's very naïve."
Cassandra, who is due to get married in February, will now spend the next two months in prison awaiting trial. She could be given the maximum penalty of 20 to 25 years.
This article originally appeared on marie claire.