(CNN) A British woman who says she was carrying painkillers for her ailing partner was sentenced Tuesday to three years in prison and fined the equivalent of $5,611 by an Egyptian court.

Laura Plummer, 33, was arrested on October 9 at Hurghada International Airport on the Red Sea after police reportedly found 290 tablets of tramadol in her suitcase.

Plummer, a shop assistant from Hull in east Yorkshire, was charged with drug possession and smuggling. Her lawyers argue the traveler misunderstood a question in court and gave a response that appeared to be a confession.

While tramadol is legal in many countries as a prescription painkiller, it is illegal for a private individual to sell it in Egypt, where it is popular among lower-income sectors.

Plummer said she had brought the drug to her Egyptian husband, Omar Abdel-Azim, who suffers from back pain.

The pair met five years ago in the Red Sea resort town of Sharm el-Sheikh, when Abdel-Azim worked as a lifeguard.

They were married in 2014 through an unregistered contract, known in Egypt as an "urfi" marriage. Plummer has been visiting her husband regularly since.

A look at the court case

In court, Plummer's lawyers argued the drug was not listed as illegal in the UK travel advisory.

The UK's decision to add a warning against carrying tramadol while traveling to Egypt was issued in November -- a month after the arrest.

"For someone to be found guilty of drug smuggling they have to be aware that they are possessing narcotics," Plummer's lawyer, Mohamed Othman, told Reuters.

"Laura did not know that what she was carrying was a narcotic. This is pursuant to that tramadol 50mg is a painkiller in her country, England. When she brought the tramadol, she believed it was a painkiller."

Othman told CNN that the sentence was light, considering the charges.

In a statement, the British Foreign Office said it "will continue to provide assistance to Laura and her family following the court ruling in Egypt, and our embassy is in regular contact with the Egyptian authorities."

An appeal is planned

Plummer's trial started in the town of Safaga on Monday with what her lawyers described as a mistaken confession.

Their client was asked whether she was intending to sell the drug. But she thought she was asked whether she simply possessed it, and said yes, the lawyers said.

The defense also rejected allegations of smuggling and trading charges. "She had only 320 pills. Even the plane ticket is almost double the price of those pills," Othman said. "It is illogical that she will deal in tramadol."

Drug smuggling convictions sometimes carry the death penalty; others carry a minimum of 10 years in prison. It wasn't immediately clear whether Plummer was convicted for possession, smuggling or both.

Plummer plans to appeal the sentence.

"It will take a while and she has to go back to the prison," said Plummer's mother, Roberta Synclair.

"It's not fair," Synclair said. "I was worried about her staying in the police custody; now she will be in the prison with criminal people."

'Terrible mistake'

Plummer's local MP, Karl Turner, said her case had been raised with British Foreign Secretary Boris Johnson and Foreign Office Minister Alistair Burt.

"I am hopeful that good sense will eventually prevail," he told the BBC.

"This is a damning indictment actually of the Egyptian authorities, in the sense that good sense and fairness certainly hasn't prevailed in this case.

"This is a decent woman who has made a terrible mistake who shouldn't be incarcerated in any prison, never mind an Egyptian prison."