Mrs Sisulu rose to prominence in 1956 when she played a leading role in a mass protest against racism laws in the city of Pretoria, then the citadel of white power.
Her political career reached a peak in 1983 when she was elected co-president of the United Democratic Front, then the internal wing of the banned ANC.
The apartheid regime detained and put Mrs Sisulu under house arrest on numerous occasions, but she remained resolute in her commitment to the anti-apartheid struggle.
"She was very brave," Ms Tolashe told the BBC's Network Africa programme.
Working as a nurse in between her activism, Mrs Sisulu remained loyal to her husband, Walter, while he was jailed for nearly 30 years on Robben Island with Nelson Mandela.
The twice-divorced Mr Mandela once recalled that the Sisulu couple shared a "generosity of spirit".
"Because they as a couple were totally giving of themselves, they have at all times been secure in their relationship," Mr Mandela said.
BBC News - Albertina Sisulu: South Africa loses a moral compass