"The story is really heartbreaking in depicting their relationship," says Wood.
"It was hard to put yourself there. It was hard to be so mean to Kate. I don't think Veda had ever felt genuine love.
"Mildred doesn't really know who she is and why she is so angry."
It was the most intense role of Wood's career. "There's not a shred of me in Veda, not the way she moves, not the way she talks and definitely not the way she thinks. That's a very good thing. I was working for two months before shooting, practising the piano and the 1930s' dialect and opera singing - even if I was being dubbed it was hard. I am a singer but you have to train your whole life to sing opera. I didn't listen to any other music while I was filming."
Wood had never done screen nudity before Mildred Pierce. Winslet gave her some coaching.
"I was going to chicken out, but we had a long talk about it and I went ahead with it. Kate has done everything so she really put it into perspective for me and I realised how important it was for the film and especially for that moment in the story and I am so glad I did it. She was there off camera giving me the thumbs up and looking at the monitor and telling me how everything looked, so it was funny."
And Woods will also be seen in the George Clooney political thriller The Ides of March where she plays an intern on Clooney's presidential campaign in a movie also starring Ryan Gosling, Philip Seymour Hoffman and Paul Giamatti.
"George offered me the movie when I was on the set of Mildred Pierce," she recalls. "It was completely out of the blue, but it was like we had already known each other for years. So of course I accepted. I loved that he was making a film that wasn't afraid to make people uncomfortable or ask difficult questions. It challenges the audience."
LOWDOWN
Who: Evan Rachel Wood
What: Mildred Pierce, starring Kate Winslet and Guy Pearce
When: Starts on SoHo from Friday December 9, 8.30pm
Also: Starring in The Ides of March, opening February 16
-TimeOut