"It definitely opened my eyes to a lot. And I certainly won't be naïve about those things," Foy said in an interview on Monday in Las Vegas.
"It's really opened my eyes about what I am allowed to have an opinion about, and what I'm allowed to stand up for myself about. And I think that's really changed my approach to myself and other women in this industry. It's been only a positive thing — even though, embarrassing."
A producer disclosed last month that Foy, who starred as Britain's Queen Elizabeth II, was paid less than Matt Smith, who played Prince Philip, because Smith was better known.
The gender pay gap has become a big issue in Hollywood after revelations that many female stars have been paid less than their male counterparts. Foy and Smith are being replaced by older performers in the next season of the show.
Foy was in Las Vegas promoting The Girl in the Spider's Web, which completed filming this month. It's based on the fourth book in the popular Millennium series revolving around hacker Lisbeth Salander, previously been played in movies by Noomi Rapace and Rooney Mara. Swedish Author Stieg Larsson, who died in 2004, created the series, and and the fourth installment was written by David Lagercrantz.
Foy said she hadn't sought their blessing before beginning her work.
"I mean, we are all actresses. We all know the game. I don't doubt for a second that those two incredible actresses don't both hate me and also ... "
Director Fede Alvarez interjected that he did indeed get Rapace's blessing.
"I met her at the premiere of her last movie and we got introduced and I told her what I was doing and she really wished us good luck and she knew you were doing it," he said.
"You got her blessing? Did you? He never told me this," Foy said, laughing. "Oh, well there you go. One down! One to go."
The 34-year-old actress says she exercised intensively to play the character — and got a new hair style.
"I got an undercut, which is something that I never thought I would have in my life. Which is great! Then all her tattoos and just how she moves and the clothes that she wears. I loved being her every day, actually. It was very liberating thing," Foy said. "Because I didn't have to worry about being attractive or being liked or any of that nonsense that women quite often have to wake up every day thinking how does the world see me? And it was really nice to wake up and just be like, like this. What you see is what you get. I quite enjoyed that."
The Girl in the Spider's Web is set for release in November.