In the movie, Monroe is portrayed as an actor ridden with anxiety or on the verge of a breakdown whenever she's on the set. Part of the reason, the film suggests, is because Monroe was a perfectionist in her pursuit to embody the role she was playing.
There are testimonies that suggest some of this is true.
In an interview with The Los Angeles Times, Don Murray, Monroe's co-star in the 1956 film, "Bus Stop," said that Monroe was determined to prove she was a "serious actress," but she was also very nervous behind the camera and often several hours late to the set.
"That was very strange, that lack of discipline," he said.
Murray also recalled how she had trouble remembering her lines and sometimes broke out into a rash.
"I think it was a lack of confidence," he said. "For somebody who the camera loved, she was still terrified of going before the camera and broke out in a rash all over her body."
Other colleagues testified to Monroe's work ethic while also struggling on the set.
"I never saw anybody work so hard," Mitzi Gaynor, Monroe's co-star in "There's No Business Like Show Business," told The Times. "She did such a good job and personally, I think she stole the whole damn show. I just think she was thrown into a nest of vipers."