The Six Rules of Maybe  (English, audio cd, Teri Clark Linden, Deb Caletti)

Scarlet spends most of her time worrying about other people. Some are her friends, others are practically strangers, and then there are the ones no one else even notices. Trying to fix their lives comes naturally to her. And pushing her own needs to the side is part of the deal.
So when her older sister comes home unexpectedly married and pregnant, Scarlet has a new person to worry about. But all of her good intentions are shattered when the unthinkable happens: She falls for her sistera (TM)s husband. For the first time in a long time, Scarleta (TM)s not fixing a problem, shea (TM)s at the center of one. And ignoring her feelings doesna (TM)t seem to be an option. . . .
This beautifully crafted novel by National Book Award finalist Deb Caletti is about crossing that blurry line between helping other people and hurting ourselves a \" and how to step back over it.