The actress plays the heroine Becky Sharp, and she tries to escape poverty and expand the heights of British society in the upcoming adaptation of William Mekepes Sacre.
Cook, 24, said she had never crossed the “six-month shooting” corset.
“No wonder women want to be liberated. The corset is suffocating. The first thing you do in the morning is shackles, and then you are ready for 13, 14 hours,” she said.
“This also limits your appetite. I lost so much weight… they are too uncomfortable.
“Women must wear so many things.
“So many things seem to be superfluous.”
The Ready Player One star said that the costume was even hard to sing in one of the ITV episodes and added: “It’s hard because you are tied up by a corset.
“The songs of that period were very high and docile.”
Cook admitted that he was nervous after the TV adaptation of “Vanity Fair” for the first time in 20 years. The TV was adapted in 1848.
“After getting the joy of this role, I felt an urgent fear and actually had to play her,” she said.
“You want to be right. But you don’t want to repeat the Becky version you have done before.”
She added: “When I was shooting on the first day, I was really nervous. I am sure I can’t take action.”
The new drama also includes Martin Clunes, Frances de la Tour, Suranne Jones, Michael Palin, Johnny Flynn, Simon Russell Beale, Tom Bateman and Claudia Jessie.
Director James Strong said: “Vanity Fair is a story with a strong female heroine. She does not compromise and hopes to be equal in a male-dominated society. This feeling is very relevant to what is happening today. This is more than ever. More general stories.”