The American Sniper star said after seeing Emma in the show, the Birdman star gave her some advice before she started the role herself. "Emma was on hand and has remained on hand and has been completely open and brilliant and just is such an amazing person," she told Vanity Fair.
"She warned me of the challenges and pitfalls that she felt," she continued. "Talked me through stamina and gave me vitamin infusion numbers. And left me throat spray and stuff and all of the things that got her through the show. It was really sweet." Emma and Sienna were also spotted catching up on the red carpet at the Oscars.
As far as why Sienna wanted to get involved with the Broadway production, she said, "I think, more than anything, I was desperate to get back into the theater. I hadn't actually ever seen a production [of Cabaret] when I signed on to do it, but obviously had heard amazing things about it, and amazing things about the people involved, and Alan [Cumming] obviously is completely iconic in that part."
"It turned out there would be six weeks that hadn't been filled [for Sally]," she continued. "It just felt like a great opportunity to come and sing and dance on Broadway and not have to be a trained singer and dancer. [Sally's] just a pretty incredible character to get to dive into. There was absolutely no reason to not do it, basically."
Sienna made her debut in the Broadway play Feb. 17 and will continue to appear in it until the show's March 29 closing.