· In her first interview, Tali Fahima talks of life in jail · Activist says she refused to work for secret service

They said they wanted to teach her to be a "good Jew" as she sat with her arms handcuffed to the legs of her chair for 16 hours a day.

But if Tali Fahima was not prepared to be a good Jew then Shin Bet, the Israeli secret service, was determined to put her in jail for as long as possible regardless of what she did.

Ms Fahima, 30, was released from jail on Wednesday after serving almost 30 months in jail for travelling to the West Bank, meeting an enemy agent and translating a simple army document.

"My first crime was that I refused to work with Shin Bet, the second was that I insisted on going to see the Palestinians and the third was that I protested against the Israeli policy of assassination," Ms Fahima told the Guardian in her first interview since her release.

For nine months of her incarceration she was kept in isolation, without access to any distractions such as books or television. "I used to lie on my bed and think about Jenin, the people I met and wonder how things were going there. I never get bored on my own," she said.

Eventually, Ms Fahima was persuaded by her lawyer to agree to a plea bargain which would mean her serving only 10 months more than the 19 she had already served. It could take as long as a year to be found innocent, she was advised.

She is unbowed by her experience. "I learnt about the nature of Shin Bet, how they terrorise us, both the Israelis and Palestinians. I learnt about the nature of the government, how they do not want us to see what is going on in our name," she said.

Ms Fahima had been an apathetic legal secretary who voted for the rightwing Likud party and carried Israeli prejudices about Palestinians until in 2003 she decided she wanted to understand why the Palestinians were attacking Israel.

She began making regular visits to Jenin, which had been devastated in an Israeli raid earlier that year. She talked to hundreds of people including Palestinian militants and for the first time heard the Palestinian view of the intifada and the difficulty of life under Israeli occupation.

Her meetings with one militant, Zakaria Zubeidi, stood out. Zubeidi was the leader of the al-Aqsa Martyrs Brigade in Jenin whose mother and brother had been killed by the Israelis that year. In countless interviews with journalists, including Israelis, he described how he and his mother had been involved in an Israeli-Palestinian theatre project which was the basis of an internationally-acclaimed Israeli documentary, Arna's Children.

A week before Ms Fahima was arrested in August 2004 she received a phone call from a Shin Bet agent who inquired how she was finding life without work before inviting her to a meeting at her local police station in Kiryat Gat in the south of Israel. She decided not to go. In the month-long interrogation that followed her arrest she was questioned about the people she had met and asked for information which Ms Fahima said she did not have. During this period Shin Bet agents briefed Israeli journalists she had been having an affair with Zubeidi, who was well known to Israelis from newspaper interviews.

"It was a Shin Bet tactic to make me and him seem bad and to delegitimise us both," she said, adding that while it was obvious to some that it was malicious, many, including friends, believed it.

When she was finally charged she was accused of translating an army document which apparently detailed an arrest operation that was due to take place.

"In the wake of the explanations of the accused," read the charge sheet, "Zubeidi later ordered the wanted persons to hide until the conclusion of the military operation and the wanted persons, who carried out Zubeidi's directive and hid, were not detained."

The document contains three aerial maps of Jenin, and four photographs of wanted men, including Zubeidi, with a short description of each. Zubeidi speaks and reads Hebrew after years of work and imprisonment in Israel.

Timeline

August 8 2004 Tali Fahima arrested

September 2004 Placed under administrative detention

December 2004 Charged with "assistance to the enemy at time of war"

January 2005 Tel Aviv district rules Ms Fahima should be placed under house arrest during the trial

January 2005 Jerusalem's high court overrules district court saying she "identifies with an ideological goal"

December 2005 Ms Fahima pleads guilty to meeting and aiding an enemy agent and entering Palestinian territory

January 2006 Ms Fahima released