Rose Feller (Toni Collette) was always the serious responsible one and Maggie Feller (Cameron Diaz) was always the fun party girl being looked after by someone else; usually Rose. This is how it had always been. But when a misunderstanding comes between the two sisters, the girls find themselves torn apart. While separated, Rose falls in love, and Maggie finds a grandmother the girls didn't know they had (Shirley MacLaine). At the same time, each is facing a lot of changes at once. But they miss each other dearly. And their long-lost Grandma wants to be reunited with both girls.