Israel expelled Palestinian prisoner Hana Shalabi on Sunday to the blockaded Gaza Strip as part of a compromise deal that persuaded her to end her 43-day hunger strike.
Under the terms of her release the West Bank resident must remain in Gaza for the next three years.
Ms Shalabi (right) had been held in Israeli "administrative detention" for unspecified terror activity.
She was initially released last year in a prisoner swap that freed Israeli soldier Gilad Schalit from captivity in Gaza in exchange for more than 1,000 Palestinian prisoners.
But Israel locked her up again after authorities alleged that she had returned to "terrorist activity."
Ms Shalabi launched a hunger strike on February 16 in protest at Tel Aviv's widely condemned policy of administrative detention, under which Tel Aviv holds hundreds of Palestinian prisoners indefinitely without charge. She ended her strike on Thursday.
On her arrival in Gaza on Sunday she was greeted by dozens of Islamic Jihad (IJ) supporters who hoisted posters with her picture. IJ said the welcome was subdued because her expulsion amounted to a "war crime."
IJ leader Khaled al-Batsh said: "Shalabi won over the Israeli occupation, and she is coming to a part of her homeland, Gaza.
"Someday she will go back to her family and hometown in the West Bank."
Ms Shalabi said: "My feeling of freedom is mixed with pain because I am leaving my family and town. God willing, we will gain freedom and all prisoners will be free."
She is scheduled to meet Hamas Prime Minister Ismail Haniyeh and a Hamas government delegation.
The Addameer Prisoner Support and Human Rights Association and Physicians for Human Rights-Israel (PHR-Israel) issued a joint statement condemning Ms Shalabi's exile.
Both organisations "fear that, given her grave medical condition, restrictions on Ms Shalabi's access to physicians and lawyers, in addition to the prevention of family visits, were used as methods of coercion."
More than 300 Palestinians remain interned in Israel.