wishes she had Keira Knightley's life.
The 'Factory Girl' star - who is in a relationship
with Jude Law
- befriended the actress when they worked together on 'The Edge of Love' and is in awe of the quiet home life her pal has with boyfriend Rupert Friend.
Sienna said: "She and Rupert live a wonderful life. They read books and discuss topics and cook for their friends.
"It's the kind of life I aspire to - I don't know if they even watch TV.
"But don't be fooled and think she is a goody-goody. She can be a bloody good laugh."
Keira loves spending time at home and admits among her favourite things to do is spend hours baking in her kitchen or browsing markets for unique additions to her house.
She told Britain's Vogue magazine: "I really do have baking days. I make all sorts of cakes and breads.
"I love going to the markets really early to find things for my house - it's full of stuff from markets; rugs, tables, chairs, anything I can get my hands on."
Sienna also admitted that Keira is so sensible, she often has difficulty remembering that, at 25, her friend is three years younger than her.
She added: "Keira has always seemed so much older and wiser than me."