The Oscar-winning actress admires the 'Blue Valentine'star's acting abilities so much, she feels like she is already close to the 30-year-old blonde beauty.
Kate, 35, said: "From a distance, I feel as if I've actually been having a secret love affair with Michelle. She and I are quite intimate in my fantasy friendship, built on admiration and respect. I'm talking about her acting, of course!"
While Michelle may not be best friends with Kate, the actress - who has five-year-old daughter Matilda with her former fiance, the late Heath Ledger - often turns to her close confidante Reese Witherspoon, 34, when she needs practical advice.
Michelle explained in the February edition of America's Marie Claire magazine: "To give credit where credit is due, I was sharing a difficulty I was experiencing with Reese Witherspoon, and she said, 'Yes, I understand, but think about how much more difficult this would be without the luxury of a reliable, steady income."
While Michelle finds it difficult being a single mother, she does concede her wealth makes her life easier in some ways.
She said: "When things are difficult for me as a single parent, I always reflect on how much harder it would be if I didn't have money-if I couldn't afford a babysitter to go to yoga class or out to dinner with a girlfriend."