Cassie Sainsbury's lawyer has described the full extent of her distress in prison.

The lawyer of 22-year-old Cassandra Sainsbury says she is “psychologically affected” by her time in jail and spends much of her time “crying” in custody.

Sources from within El Buen Pastor prison told 9 News on Friday that Cassie is refusing to leave her cell, partly because she mistrusts the non-English speaking prison guards.

The Adelaide woman was arrested on April 12 at Bogota’s El Dorado airport in Colombia after being found with almost 6kg of cocaine hidden inside headphone boxes.

In an interview with 9 News, Ms Sainsbury’s lawyer Orlando Herran said the former personal trainer’s mental state is suffering after spending three weeks behind bars in El Buen Pastor, one of the largest women’s jails in the country.

“I can see that she’s very affected psychologically. She [is] permanently crying, very sad,” Mr Herran said.

He added that because of this, he intends to encourage the young Australian to plead guilty so as to make an arrangement for Ms Sainsbury to serve her time back home in Australia.

“It is a possibility to make an agreement for the special case of Cassandra,” he told 9 News.

However, the judge presiding over the case rejects the possibility of that kind of arrangement.

“The system is clear – do the crime in Colombia, do the time in Colombia,” he told 9 News.

Judge Zambraro added Ms. Sainsbury is “too young” to be caught up in “something like this”.

“What caught my eye was her age, she was 22. Too young to be caught up in something like this,” he said. “But caught up in it she is, and three weeks in custody is starting to have an affect on her mental state.”

The news comes just a day after Ms. Sainsbury's fiance addressed the media for the first time since her arrest.

Scott Broadbridge voiced his strong support for the 22-year-old who he claims is innocent of the drug trafficking charges she faces in Colombia, despite acknowledging there were "unanswered questions".

In addition, he asked for privacy, taking aim at news outlets that he said were camping outside his house and harassing him and his grandmother.

Broadbridge described Sainsbury as the “delight of [his] life” and reiterated his intent to marry her while addressing the media and public on Thursday morning.

"It is extremely stressful for her but we are able to talk every day and that is a great comfort for both of us," Broadbridge said.

"She is concerned about the conditions of the jail, which are not ideal, and it's very difficult for her not knowing anyone in the country."