NEW YORK TIMES BESTELLER Conversations between sisters reveal a deep and constant tug between two dynamics--an impulse toward closeness and an impulse toward competition. It takes just a word from your sister to start you laughing, or to summon up a past you both share. But it also takes just a word to send you into an emotional tailspin. For many women, a sister is both a devoted friend and a fierce rival. Wise and witty, You Were Always Mom's Favorite...