South African activist Winnie Mandela has passed away at the age of 81 due to many years of being sick.

Mandela affectionately known as “Mama Winnie” was married to the human rights icon and former president of South Africa Nelson Mandela from 1958 until their divorce in 1996. For 27 years of their marriage, he was imprisoned by the minority-white apartheid regime.

The couple separated after Nelson Mandela’s release in 1990, and he became president of South Africa in 1994. He accused his wife of infidelity. After the divorce, she kept his name and added her maiden name. Nelson Mandela died in 2013.

“She kept the memory of her imprisoned husband Nelson Mandela alive during his years on Robben Island and helped give the struggle for justice in South Africa one its most recognizable faces,” the family said.

“She dedicated most of her adult life to the cause of the people and for this was known far and wide as the Mother Of The Nation,” it said.

Her controversial reputation stemmed from harsh comments that appeared to promote violence and were critical of her famous ex-husband, along with accusations of murder and a conviction for bank fraud.

Jesse Jackson, the American civil rights leader, told USA TODAY that the former South Africa first lady was a “huge force” in the Free South Africa movement who deserves credit for helping to keep the anti-apartheid push strong during her husband’s 27 years in prison.

“She was the face and voice of the movement,” Jackson said of her husband’s years in prison. “It was her voice and her courage and her risk that kept them alive for those years.”

After apartheid ended, Mandela became a member of Parliament and served as deputy minister of arts and culture.