Our grandmother, Amina Desai, who has died aged 89, was inspirational and strong-willed, the head of a family spanning continents and generations. Her experiences under apartheid in South Africa would shape her life, and the lives of those around her.

Early one morning in October 1972, Amina was arrested, accused by the apartheid government of conspiring with her lodger, Ahmed Timol, to further the aims of the then-illegal African National Congress. Timol, a schoolteacher and family friend, had been staying with her and was arrested just days before, but was tortured and killed in detention, becoming one of the many detainees to mysteriously "jump" from the 10th floor of the John Vorster Square prison.

That November, Amina was sentenced to five years' imprisonment. She served most of her sentence alongside the longtime ANC stalwart Dorothy Nyembe, and for a short while with Winnie Mandela, whose defiance and courage she greatly admired. She was released in 1978; by then she was South Africa's longest-serving Indian woman political prisoner, and was placed under a banning order and house arrest for a further five years.

Born Amina Nagdee in South Africa, one of nine children of a Malay mother and Indian father, she was obliged to leave school aged 10 to look after her younger siblings. Intent on becoming a nurse, she enrolled herself in a school for midwifery, until she was unceremoniously taken home by her father five days later, who deemed it an unsuitable profession. She persisted with her education, however, and was eventually allowed to study at Harvard College, in Johannesburg, which at the time was "whites only". Amina became the only non-white student, attaining qualifications in typing, commerce and shorthand.

In 1943 she married Suleiman Desai. He was a key member of the Transvaal Indian Congress, then engaged in a passive resistance campaign against the apartheid government. Desai was also owner of an agency for Watson's shoes, a large local brand; when he died in 1969, Amina immediately assumed control of her husband's business, undeterred by being a woman in a male-dominated profession, and ran it successfully for the next 35 years.

She was devastated to leave South Africa in 2004, as failing health brought her to live with her children in the UK and Ireland, where they had sought refuge from apartheid in the 1970s. Amina died peacefully in Dublin, where only a few weeeks before she had attended Freedom Day celebrations hosted by Priscilla Jana, the South African ambassador to Ireland, who had been part of Amina's legal defence team.

She is survived by her four children, Adela, Bahiya, Hilmi and Zureena, and 12 grandchildren, including us.