“She said, apparently, she was glad it was me,” Bonham Carter said. “My main thing when you play someone who is real, you kind of want their blessing because you have a responsibility.”
Season 3 of the series kicks off on November 17.
It spans the portion of Queen Elizabeth II’s life and reign from 1963 to 1977.
Bonham Carter stars as her younger sister and said she researched for the role, including talking to a psychic and an astrologer.
The star had a question for Princess Margaret, who died in 2002 at the age of 71 following a stroke.
“So I asked her: ‘Are you OK with me playing you?’ and she said: ‘You’re better than the other actress’ … that they were thinking of,” Bonham Carter reportedly said. “They will not admit who it was. It was me and somebody else.”
The actress said that made her think the deceased royal was present, because she was known for being “really good at complimenting you and putting you down at the same time.
“Then she said: ‘But you’re going to have to brush up and be more groomed and neater,'” Bonham Carter said. “Then she said: ‘Get the smoking right. I smoked in a very particular way. Remember that — this is a big note — the cigarette holder was as much a weapon for expression as it was for smoking.'”
Bonham Carter also reached out to some living folks, she said, talking to some of the princess’ inner circle.
“Three ladies-in-waiting, a couple of relatives, a very close relative and some really close friends,” she said. “They loved the woman and were very happy to talk about her because they miss her.”
CNN has reached out to a rep for Bonham Carter for further comment.