Sandra Oh mentions working with (or not) Nicole on Rabbit Hole in a new interview with screencrave.com:

Speaking of talented and gracious collaborators, the majority of your scenes in Rabbit Hole are with Aaron Eckhart. How was it working with him?

SO: I respect his acting so much and to be able to have had scenes with him. There are so many reasons why I wanted to do this piece but it was basically because the script is so stunning it’s insane, and John, and then Nicole and Aaron. For me being a fan of Aaron’s work for a long time, being able to act with him onscreen — I jumped at the opportunity!

You didn’t really have that many scenes with Nicole Kidman as an actress but did you get to interact with her as a producer?

SO: I didn’t really have any interaction with her as a producer because during her time on set she was acting. She was in her acting head. But I also knew that Nicole had a hand in deciding and choosing people. Hopefully, she was pleased with her choice of me as Gaby.