Anne Hathaway and Rosemarie DeWitt's

DeWitt's Rachel is the somewhat uptight older sister of Anne Hathaway's Kym, who is a bit of a loose cannon. We find out when Kym is brought home from her latest stint in rehab in order to be present for the weekend leading up to Rachel's wedding, a tumultuous period in which long-suppressed conflicts, issues and tragedies from the family’s past rise to the surface.

Rosemarie DeWitt is best known for her work on stage and television, she is currently at the center of growing Oscar buzz for her supporting performance as the title character in a big screen production, Jonathan Demme's critically-acclaimed "Rachel Getting Married."

How Rosemarie DeWitt and Anne Hathaway decided to conduct their relationship off-screen, in consideration of their relationship on it...

"We had one dinner beforehand, and I think we were already starting to inhabit our characters a bit, and it was very polite and nice. And then I think our instincts were to not become buddy-buddy — sometimes that works, you know, sometimes you need that to be able to finish each other's sentences — but I think we would have been in danger of maybe diffusing the necessary tension between these two women. So we sort of just maybe had a little bit of chat in the morning before we started and then, you know, I had my iPod in probably for the rest of the day."