Madikizela-Mandela was responding to a request from Luthuli House to meet with the family to discuss Tuesday's ANC centenary celebrations, which will see Zuma delivering a lecture on Nelson Mandela.
In email correspondence, addressed to ANC spokesperson Jackson Mthembu – which the Mail & Guardian has seen – Madikizela-Mandela said the family "rejected" the ANC's request for a meeting for a number of reasons but that "hundreds more" existed.
Madikizela-Mandela said in the past the ANC "never had any interest in celebrating Tata's [Mandela's] birthday except to gate crash on the family's arrangements" and that its attitude towards the family proved that "we do not matter at all".
"The family is still grappling with the most shabby treatment throughout the years, especially in Mangaung in January this year. As I indicated we are deeply hurt as the family. We did not even have a table and the situation was saved by Mrs Bridgette Radebe," wrote Madikizela-Mandela.
"No one has cared to establish how we are doing as a family. It is quite clear that we do not matter at all, we only do when we have to be used for some agenda," she said.
Madikizela-Mandela said she was "surprised" when the ANC approached her to be part of the centenary celebrations because "in 2011 when you were preparing for 2012, I was a spectator throughout".
"I was not deployed anywhere. I am the one person who has first information about the leaders you are celebrating. I would have even given you the song that was composed for that day," she wrote.
Madikizela-Mandela took issue with the fact that no official from Luthuli House was present when the centenary flame, which has been making its way around the country, was brought to her and that instead the national leaders left the job to the provincial leaders.
"It was clear that a certain faction fought for it to be brought to me. I am aware that [Arts and Culture] Minister Paul Mashatile, [who is also the ANC Gauteng chairperson] and Cde David Makhura [ANC Gauteng secretary] fought for it to be brought to me.
"Even more alarming was that the manner in which the centenary flame was brought to Tata left much to be desired.
"There was no parade of the soldiers as there was to me. It was clear that it was done for someone's ego, not to the family."
Madikizela-Mandela condemned the ANC for purporting to care about her well-being, when neither Zuma nor Mthembu visited her when she was hospitalised, let alone called her to wish her a speedy recovery.
"I have been in and out of hospital since January 25 this year, not even one phone call from Luthuli House. Instead you [Mthembu] gave an interview saying I was recuperating from an ankle operation when you did not even care what kind of an operation I had. I never had an ankle operation, I had a knee operation," she said.
Mthembu said the ANC would not comment on private correspondence between the party and the families of former presidents.
He said a representative of the Mandela family would be present during Zuma's lecture on Mandela on Tuesday, but refused to say whom. But the M&G understand that both Madikizela-Mandela and Mandela's grandson Mandla Mandela have refused to attend.
Meanwhile, dozens of Zuma supporters have been bused in from KwaZulu-Natal and Mpumalanga to Limpopo for the Mandela lecture on Tuesday.
The M&G has been reliably informed that Zuma's organisers have ensured the hall will be packed with ANC members sympathetic to his leadership and that his detractors from the hostile province, home to expelled ANC Youth League leader Julius Malema, will not be present.
En route to the lecture, just outside of Polokwane, the M&G spoke to delegates being transported in a minivan from KwaZulu-Natal. The delegates confirmed that they were handpicked by the KwaZulu-Natal provincial leadership to travel to the lecture to "support our president".
"We will not sing divisive songs. We are here to do our job and that's to support our president," said one ANC member, who asked not to be named.
The group of about 10 men said more buses were en route to the venue where Zuma was expected and that others were expected from Mpumalanga.
This is Zuma's first public appearance in the Limpopo province in months. He refused to attend the Limpopo provincial conference late last year, where Limpopo premier Cassel Mathale was re-elected to the position of ANC chairperson.
In the run-up to the conference, Zuma's ally ANC Mpumalanga chairperson David Mabuza had allegedly pumped millions of rands into the province to influence delegates to vote against Mathale to ensure that a leader sympathetic to Zuma was elected.
However, under Mathale and with the support of his political ally, Malema, the province has been at the forefront of pushing the campaign for Zuma to be replaced by Deputy President Kgalema Motlanthe at the party's elective conference in Mangaung in December.
Mthembu said it was not unusual for a party event to be attended by other provincial members.
"At any rate the ANC gets people from everywhere. Like the lecture in Gauteng was attended by members from KwaZulu-Natal and Gauteng and other places … To us it's not an issue as long as we have good cadres of the movement [at the lectures] … and that we don't have people [from one area] who overpopulate the lectures," he said.
Zuma was expected to deliver his Nelson Mandela lecture at 6pm on Tuesday.