Condolences poured in on Twitter for anti-apartheid activist Winnie Madikizela-Mandela, who died at 81.

Mandela, who was a controversial figure, was once married to former South African President Nelson Mandela. Most of their marriage occurred when Mandela was imprisoned on Robben Island.

RelatedWelcome home: Mandela honored on visit to Atlanta

RelatedAtlanta mourns Nelson Mandela

Winnie Mandela was a force to be reckoned with in her own right.  She was known as “Mother of the Nation” or  simply “Mama.” While she could be polarizing, Mandela remained beloved by many.

A spokesman said Mandela, a trained social worker, had been ill for a while and died in Johannesburg surrounded by family and loved ones.