Suspended African National Congress (ANC) secretary general Ace Magashule said Jessie Duarte died with some of the party's top secrets.
Magashule made the comments at Duarte's funeral on Sunday.
The 68-year-old died in the early hours of Sunday morning after an 8-month battle with cancer.
She was buried on the same day as per Muslim rites.
Duarte's funeral was attended by the governing party's top brass, who all hailed her for her commitment to renewing the embattled party.
Magashule revealed to journalists that the pair often visited former president Jacob Zuma.
But he wouldn't be drawn on further details of the discussions that they held with Zuma behind closed doors.
"We have visited comrade Zuma several times with comrade Jessie and this is where I'm telling you some of the things that she said please keep some of these secrets of the movement. If these secrets come out, there is no more anything else."
Zuma has sent his condolences to Duarte's family announcing plans to share more details on their relationship.