Sitting on a bed in the family house, surrounded by posters that commemorate the death of her son, Subhaia Musa Abu Rahme laments her latest loss. Jawaher, her 35-year-old daughter, died on New Year's Day after collapsing in her home village of Bil'in during a demonstration against the Israeli separation barrier. Despite assurances to the contrary from the Israeli army, her family insist that she died after inhaling massive quantities of tear gas.

"How do you think I feel?" says Abu Rahme softly, a white scarf covering her head and an almost absent look in her eyes. She can hardly comprehend what has happened to her family or the repeated horrors that have been inflicted on it. The family has come to symbolise the Palestinian struggle against the occupation of the West Bank.

Last year, Abu Rahme's son, Bassam – a charismatic member of the committees that organise "non-violent resistance" against the barrier – died after being struck by a gas canister at a demonstration. Another son, Ashraf, has been left with a limp after being shot at close range with rubber-coated steel bullets by an Israeli soldier. And now, Jawaher.

"She was the nicest girl in Bil'in. Here, everyone liked her. The wall confiscated our lands, and now my children are gone. I have nothing left", says Abu Rahme, a 55-year-old widow.

"But every time we lose someone we love, we gain strength to fight against the occupation," she adds. "This is our land and we are going to defend it. We will not stop until we tear down the wall."

Outside the house, on the patio, a group of men mourn Jawaher. They eat dates, drink spiced coffee and chain smoke – but barely speak. Next door, the women gather in a separate room, as tradition dictates. Political delegations, friends, relatives and schoolchildren pass by to express their condolences for the kind-hearted young woman who had worked as a carer for two disabled children in nearby Ramallah.

From the Abu Rahmes' neighbourhood, the barrier that separates the Palestinian territories from Israel – and which cuts off the famil y from its olive groves – is clearly visible. For more than five years, they have participated with their neighbours in the struggle against the construction. But for them, more than for any other family in the village, the battle has brought tragedy. And last week, Jawaher's death returned them to the headlines.

Her family are adamant she died after inhaling the tear gas fired by Israeli soldiers during the demonstration in Bil'in. The army questions the reliability of Palestinian reports, including the hospital documents, and has complained in a statement of "lack of co-operation with the Palestinians". It also says that although the army inquiry has not yet been completed, "a number of scenarios have been posited, among them the possibility that Abu Rahme's death was entirely unrelated to the demonstration last Friday."

For a visibly exhausted Subhaia Musa Abu Rahme, there is no such doubt.

"I was with my daughter, a bit far away from where the clashes were taking place, when the soldiers started shooting gas," she remembers. "The wind brought the gas. We were very affected. I was feeling bad when my daughter told me that she could not take it any more and started vomiting." Another of Jawaher's brothers, Samir Ibrahim, 34, recalls calling an ambulance to take his sister to the hospital in which she later died.

"She was in a very bad condition," he says. "They took her to a house and she was vomiting foam from her mouth. In four or five minutes, an ambulance came. They [the doctors] told us that she lacked oxygen due to the gas."

Every Friday, Samir attends the demonstration against the Israeli separation barrier, built in the aftermath of the second intifada.

Clashes at the protests are common, with some Palestinians throwing stones and the army shooting tear gas, a fetid liquid known as skunk and employing other crowd dispersal weapons. A dense cloud of smoke fills the air and spreads over the village within seconds. It is not unusual for people to vomit in the streets, their eyes burning from the tear gas. But still, Samir, his family and friends keep up their display of defiance.

"We go to show our suffering," he says. "It is our way to denounce that they are raping our land." When asked if the hardships his family has gone through make them special, he says no. "We are like the others. This is only a test from God."

Bil'in, about two miles from the 1967 armistice border, or Green Line, has always been an agricultural village. But the villagers, according to Michael Sfard, the Israeli lawyer representing them, are now prevented from getting to about 50% of their farmlands by the barrier. The impoverished Abu Rahmes are among those who lost their land.

Like the rest they can, in principle, enter their groves through a gate that the army is obliged to open for a certain number of hours a day. However, according to Sfard, the army does not always comply.

Back in the family home, Ashraf, the brother who was shot two years ago, listens attentively to his mother and Samir, a red-and-white Palestinian scarf tied around his neck. His shooting was filmed by an Israeli human rights group and the images travelled around the world. He considers himself lucky; not only did he escape with relatively minor injuries, but the lieutenant-colonel who ordered the shooting is now being judged in a military court. But last week there was no reason to be cheerful. "Our family is destroyed," he says. "There will always be sadness in our family."