Davis, 63, penned an emotional open letter to Will Ferrell, who is set to play President Reagan in the film, which will reportedly focus on the former president's battle with Alzheimer's. In her letter, Davis criticizes the actor for treating the subject matter insensitively.
She suggests that perhaps if Ferrell knew more about the disease, he would not make it the plot of a comedy film.
"Alzheimer's doesn't care if you are President of the United States or a dockworker," she wrote. "It steals what is most precious to a human being – memories, connections, the familiar landmarks of a lifetime that we all come to rely on to hold our place secure in this world and keep us linked to those we have come to know and love."
Davis recalled having to watch her father succumb to the disease, slowly losing the essence of who he once was.
"I heard his voice tremble as he stood in the living room and said, 'I don't know where I am.' I watched helplessly as he reached for memories, for words, that were suddenly out of reach and moving farther away," she wrote. "For ten long years he drifted – past the memories that marked his life, past all that was familiar ... and mercifully, finally past the fear."
Davis said she wanted to make one thing clear: "There was laughter in those years, but there was never humor."
"Perhaps for your comedy you would like to visit some dementia facilities," she challenged Ferrell. "I have – I didn't find anything comedic there, and my hope would be that if you're a decent human being, you wouldn't either."
She concluded by asking Ferrell to explain his reasoning behind the film: "Perhaps you would like to explain to them how this disease is suitable material for a comedy."
Reagan announced in 1994 that he had Alzheimer's, and he died nearly a decade later, on June 5, 2004
When news of the film was released, Reagan's son, Michael, was also one of the first to react.
#Alzheimers is not a comedy to the 5 million people who are suffering with the decease,it first robs you of your mind and then it kills you— Michael Reagan (@ReaganWorld) April 29, 2016
"Alzheimers is not a comedy to the 5 million people who are suffering with the decease, it first robs you of your mind and then it kills you," he wrote.
The film reportedly takes place during the beginning of President Reagan's second term. In it, he "falls into dementia," according to the Black List, an annual survey of notable new screenplays, reports The Hollywood Reporter. "An ambitious intern" is then "tasked with convincing the commander-in-chief that he is an actor playing the President in a movie."