Mendes had Parkinson's disease, she says, diagnosed more than 10 years ago.
"He was a brilliant man, a talented artist and a real American hero, and I'm going to miss a lot," Fletcher said.
He will be buried in Nevada, where his family is, she said.
Fletcher added that Mendes, the author of several books, died writing all the stories he wanted to tell. He and his wife, Jonah Mendes, had just sent their most recent book to the publisher, she said.
"Moscow's rules: CIA secret tactics that helped America win the Cold War" is scheduled to be released on May 21, writes the publisher of PublicAffairs on its website.
Aflek paid homage to Mendes on Saturday, calling him "a true American hero" who "never sought the light of his actions (but) just wanted to serve his country." In 2012, Mendes told CNN that he was the head of the CIA branch for identity certification in 1979. And we will work on preparedness around the world, ready to deal with the interior, for example, that I will knock on your door at midnight and say that I want to defect, "he said.
Mendes devised a plan to create a fictitious sci-fi film called "Argo" to be filmed in Tehran. agreed to give passports to the six Americans.
In January, Mendes and others flew in Tehran under the guise of scouting locations for the film. Mendes directed Americans who fled through immigration at the airport.
"We always say that there is nothing so wonderful as the feeling of wheels. In this case, we have still been in the Iranian airspace for a while, so all kept their breath until we had left the country completely. According to Biography, Mendes has worked for the CIA for 25 years. He met Jonah, his second wife and former CIA officer while working in Russia in 1980.
Steve Almasi of CNN contributed to this report.