"I have faith he's going to recover. It's hard," she added. "I love him."
The government has not given details about the treatment Chavez is undergoing, and hasn't identified the type or exact location of the tumors that have been removed from his pelvic region.
Venezuela's opposition has demanded the government provide more specific information about Chavez's condition, and has criticized a decision by lawmakers last month that indefinitely postponed his swearing-in ceremony for a new six-year term.
Two prominent Venezuelan jurists asked the Supreme Court on Thursday to determine whether Chavez is fit to remain in office. Former Supreme Court President Cecilia Sosa Gomez and professor Jose Vicente Haro called for the court to appoint a board of medical experts to determine whether Chavez is in physical and mental shape to remain president.
They argued that if Chavez is fit to be president, the court should proceed to hold a public swearing-in.
Government officials insist Chavez remains in charge and has been communicating with government officials about policy decisions and signing documents.
Foreign Minister Elias Jaua read a lengthy letter from Chavez on Friday to a gathering of African and South American leaders in Equatorial Guinea.
In the letter, which ran for about 1,500 words, Chavez said he was sorry not to be able to attend the meeting. Chavez denounced Western military intervention in countries such as Libya in recent years, and called for more "South-South cooperation."
The letter ended with the words: "We will live and be triumphant!"
Prayer gatherings for Chavez this week have included a ceremony where indigenous shamans danced on Thursday, attended by Guatemalan indigenous activist Rigoberta Menchu.
Menchu, who received the 1992 Nobel Peace Prize, said she had come to Venezuela "as one of the Maya spiritual guides" with knowledge of medicinal traditions.
"I'm completely sure that President Hugo Chavez has received the cosmic energies. He has received the strength of our Mother Earth. ... He is going to overcome big obstacles," Menchu said Friday at a televised event where she spoke alongside Maduro.
As for Chavez, she said, "He has to have sufficient rest so that he can recover the strength of his vital energies as soon as possible."
Associated Press writer Jorge Rueda contributed to this report.
Ian James on Twitter: http://twitter.com/ianjamesap