Flirty, flaky part girl Maggie (Diaz) and plain, dependable lawyer Rose (Collette) are sisters, best friends and bitter rivals who seem to have only two things in common: DNA and size 8½ shoes. Only when their love-hate relationship veers towards the hate end of the spectrum do they accidentally discover they also share a long-lost grandmother (MacLaine) who enriches their lives and helps them make peace with each other — and themselves!