"Now we are about 25 days we have been in hospital," Machel said, giving thanks for the outpouring of well wishes from around the world for the Nobel peace laureate.
"Although Madiba sometimes may be uncomfortable, very few times he is in pain," she said using Mandela's clan name.
The former president, who turns 95 later this month, was rushed to hospital on June 8 with a recurring lung infection.
"Thank you, thank you, thank you," said Machel, launching the latest in a series of events to mark Mandela's life.
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"The outpouring and humbling demonstrations of love, of care, of support, of hope are taken into our hearts every single day."
"We thank you very deeply."
Amid an increasingly bitter family feud -- involving allegations of adultery, grave tampering and siblings born out of wedlock -- Machel said Mandela's example could serve as a beacon for unity for the country.
"While he lies in hospital, he offered an opportunity for all of us again to be united," Machel said.