A New Zealand woman who is being held at a US immigration centre with her six-year-old son after they were detained crossing the Canada-US border, is being wrongly “treated like a criminal”, according to her friend and advocate.

Sarah Shaw, 33, a New Zealander who has lived in Washington state for just over three years, dropped her two eldest children to Vancouver airport on 24 July, so they could take a direct flight back to New Zealand for a holiday with their grandparents.

When Shaw attempted to re-enter the US, Immigration and Customs Enforcement (Ice) detained her and her youngest son, in what was a “terrifying” ordeal, said Victoria Besancon, Shaw’s friend who is helping to raise money for her legal fight.

“Sarah thought she was being kidnapped,” she said. “They didn’t really explain anything to her at first, they just kind of quietly took her and her son and immediately put them in like an unmarked white van.”