"We, as a family, we have been blessed to have Madiba as the head of our family. We have been blessed to have Mama as a matriarch of our family. Now, what is left of us?"These were the words of Madiba's widow Graça Machel at a memorial event which the Nelson Mandela Foundation held for Winnie Madikizela-Mandela at Constitution Hill on Monday.Madikizela-Mandela died on April 2, 2018, at the age of 81.Machel said she was there to speak about her "big sister"."It is too early, really too early for us to process the pain we have gone through. But let me say something. As a nation, we tend to wake up to realise who the people are who have made us as a nation, the people who sacrificed so much for us."WATCH: Mam' Winnie was a sincere, honest and committed worshipper - Reverend"We tend to wake up and recognise them when they leave. Imagine how wonderful it would have been for Mama to sit among us and listen to all those tributes which have been [pouring out] ever since the moment her transition had been announced," she said."Don't you think it would have been really great for her to have all the untruths, which were allowed to live with us, about her life to be cleared while she was still among us?"Machel also challenged South Africans to go out and do something good in memory of Madikizela-Mandela and to report back after a year about what they had done.When she died, she multiplied into thousands, if not into many millions, Machel said."Because of that, I want to challenge us, each one of us. If Mama was giving soup to people in Soweto, who is going to stand tomorrow and do it?"Machel added that Madikizela-Mandela had sacrificed a lot for her family and for the country.Earlier, Madiba's eldest granddaughter, Ndileka Mandela, said it was very hard for her to speak about the struggle stalwart."We called her Big Mami. We are still gutted. It is still very sore," she said."It is quite significant that this memorial is held here today, because this is the place [where] Big Mami spent time in solitary confinement. It is the same place she heard about my father's accident," she added."In life, she got a raw deal. And we want her to be buried in dignity."Ndileka's father, Thembekile, was Nelson Mandela's eldest son. He was killed in a car accident in 1969.