In the unusual case, Tali Fahima, was convicted last month in a plea bargain to avoid a life sentence on initial charges of aiding the enemy in wartime and supporting a terrorist group.
Under the deal, Fahima pleaded guilty to charges of contact with a foreign agent, informing the enemy and disobeying an order. The court in Tel Aviv confirmed a three-year sentence on Thursday.
Fahima is expected to be released in another 10 months, since she has been under arrest for more than a year.
Fahima moved to Jenin in the West Bank at the height of a five-year-old Palestinian uprising and befriended Zakaria al-Zubaidi, leader of the al-Aqsa Martyrs Brigades, the armed wing of the ruling Fatah party.
Fahima, a frequent guest at al-Zubaidi's home in Jenin, told reporters that she was staying close to the leader to protect him from Israeli assassination.
Detained without trial
Fahima was arrested last year and held for three months without trial, a measure that Israel usually reserves for Palestinians detained in the West Bank and Gaza, before she was indicted.
Prosecutors said she translated for Palestinian gunmen a secret military document which they had obtained that outlined Israeli army plans to detain or kill resistance fighters.
"I am sure that she regrets what happened in terms of the consequences but at the time she regarded it as legitimate political activity and this is how she sees it"
Smadar Ben-Natan, Fahima's lawyer, said when his client was convicted last month: "I am sure that she regrets what happened in terms of the consequences but at the time she regarded it as legitimate political activity and this is how she sees it."
Fahima, who said she once supported the right-wing Likud party, has been a critic of Israels occupation of the West Bank.
Her friends denounced the charges against her as politically motivated. But Orly Ben-Ari, prosecuting, said they were based on "very serious violations" against Israeli security concerns.