It was revealed earlier this year (20) that the former "Twilight" star would be taking on the role of the royal in the film - with the announcement dividing opinion among fans.
While many thought it should have gone to a British actress, American star Kristen has assured critics that she's doing everything she can to master Diana's English lilt.
"The accent is intimidating as all hell because people know that voice, and it's so, so distinct and particular," she told InStyle magazine. "I’m working on it now and already have my dialect coach."
Kristen added that she hasn't been "this excited about playing a part... in so long" and, ahead of shooting, she's researching the tragic ex-wife of Britain's Prince Charles as much as she can to make sure she does her justice on the silver screen.
"In terms of research, I've gotten through two and a half biographies, and I'm finishing all the material before I actually go make the movie," she continued.
"It's one of the saddest stories to exist ever, and I don't want to just play Diana - I want to know her implicitly."
The film, directed by Pablo Larrain ("Jackie", "Neruda") and written by "Peaky Blinders" creator Steven Knight, imagines a weekend in the early 1990s when Prince Charles' wife decided her marriage to the heir to the throne wasn't working.