The traits that make Becca difficult to play are counterbalanced by the causes that explain them. On the negative side, Becca is isolated and unconnected with other people. She cannot psychologically grasp how people go on with their lives in such a normal way when she is derailed from the normal aspects of life by overwhelming grief and sorrow. In order to find a way to develop the isolation and distance in her character, first fathom the pain and meaning of her grief and sorrow.
Another negative is that her sense of humor is employed against other people rather than to draw others to her and bind a relationship through a shared laugh or private amusing anecdote. Incidentally, this is another one of her traits that further isolates her. To find a way to develop this biting, unpleasant humor in her character, first fathom how small and insignificant daily troubles, pains and sorrows seem to enormous ones: first you must also recognize that troubles and suffering come in degrees of greatness and shades of horror.
Finally, recognize that under her distance, her isolation, and her caustic humor, lies the true essence of her being. On the positive side, she is truly interested in her sister's well-being, even though she nags and criticizes her. She is truly sympathetic of her mother's loss, although she sees that the circumstances of their losses may not compare. She realizes that other people's grief and suffering, especially Howie's, though having different causes (maybe lesser causes) than hers are no less painful and complex than her own: “You’re not in a better place than I am, you’re just in a different place.”
Thank you for your answer. It gave me alot of insight into her. I have a call back for her tommorrow evening. She is such an interesting character and it would be a great challenge to play her. I'm a little scared. I don't want to come off as shrewish because she is not at all. I want to figure out how to play her without playing a mood. Are you an acting teacher?