We've got some more info on Sandra Oh's character in Rabbit Hole. It is spoilerish, so if you don't want to know, don't read any further.
It is rumoured that Sandra plays a character called Gabby who has lost her child and who also almost has an affair with Howie Corbett (Aaron Eckhart) after getting acquainted with him and his wife Becca (Nicole Kidman) in a grief support group.
