Accused Australian drug mule Cassandra Sainsbury could serve six years in prison after a plea deal was reportedly struck with the prosecution.

The 22-year-old Adelaide woman was arrested at Bogota's El Dorado international airport in April, trying to smuggle 5.8 kilograms of cocaine inside 18 separate packages of headphones.

Sainsbury is facing up to 30 years in jail, but Channel Nine reported a plea deal had been struck, agreed on by both the prosecution and the defence.

The deal still needs to be signed off by the judge, who will return to the courtroom on November 1 to announce whether the deal will go through.

A spokesman for the Department of Foreign Affairs and Trade said in a statement: "Pending the final sentencing hearing, the Department of Foreign Affairs and Trade understands that Ms Sainsbury will be sentenced to six years' prison and a fine."

A submission was also put to the judge saying Sainsbury was behaving well behind bars, which means she could be free in two years if the deal goes through.

The defence and prosecution struck the same deal in July, but the judge said he could not accept it at the time.

Locked phone the key to freedom?

In an interview with Nine Network's 60 Minutes program last month, Sainsbury said she thought she had accepted a job as a legitimate courier transporting documents for $10,000 plus flights.

"I had outstanding bills, I suppose I took the risk," she said.

But at the last minute, she said the plans were changed and she was sent to Colombia where a "mastermind" known only as Angelo threatened to kill her mum, sister and fiance if she did not transport his drugs.

He sent her photos of her family on WhatsApp and those messages prove her innocence, she said.

Except, she says cannot unlock it.

"It's very true. I haven't used it for nearly six months, I'm not going to remember a pattern," she said.

Since her arrest, Sainsbury has also been accused of being a sex worker — an allegation she also denies.

"I'm not a prostitute. There was some work relating with [prostitution] Club 220, but it wasn't prostitution," she said in the interview.

Sainsbury said she worked at the western Sydney brothel as a receptionist.

Sorry, this video has expired Cassandra Sainsbury's plea deal was rejected by a judge in Bogota (Image: AP/Fernando Vergara)

ABC/AAP