Miller played the actress Tippi Hedren in the 2012 movie The Girl, which dramatised the making of Hitchcock's iconic thriller The Birds, with Toby Jones as Hitchcock.
It depicted the director as a tyrannical figure, obsessed and infatuated with the actress and later given to cruelty towards her, after she rebuffed his romantic advances.
Watch: Sienna Miller says Chadwick Boseman took pay cut for her
The abuse not only manifested itself in his direction, traumatising Hedren by filming gruelling scenes with real birds over days, but also by keeping the actress under contract.
After making movies like The Birds and Marnie with her, Hitchcock then prevented her from working for other directors.
Speaking at an online Q&A at the Montclair Film Festival (via Indiewire), where her latest movie Wander Darkly is playing, she said: “That was a really, really traumatising, appalling experience for her. And not only how he treated her in the making of those films but in the aftermath.
“He kept her under contract. He wouldn’t release her to work with Godard and Truffaut, etc. who we were all trying to hire her, but just kept her for 10 years under this contract and watched her grow old, without making anything. It was very sadistic.
“Thankfully I think the world has changed enough where if anybody even attempted that kind of abuse, there is an army of women that would come out and fight it.
“And I feel very fortunate to be working in these times, because I think that story is not uncommon of that era. You really belonged to the studio that you were assigned to and, essentially, to the director.”
Hedren revealed to biographer Patrick McGilligan in the book Alfred Hitchcock: A Life in Darkness and Light that Hitchcock purposely ruined her career, after she signed an initial seven-year contract with him.
“I said I wanted to get out of my contract,” she explained.
“He said: 'You can't. You have your daughter to support, and your parents are getting older'. I said: 'Nobody would want me to be in this situation, I want to get out'.
“ And he said: 'I'll ruin your career'. I said: 'Do what you have to do'. And he did ruin my career. He kept me under contract, paid me to do nothing for close on two years.”
Watch Sienna Miller and Chadwick Boseman on slang