Who is Caroline Gill from The Memory Keeper's Daughter and what is their importance?

Caroline Gill is an organized, capable nurse who is in love with David Henry from a distance. She bravely travels through a blizzard to help David with Norah's childbirth, and, because she is devoted to him, takes Phoebe away as he has requested. However, Caroline is in her thirties with no prospects of marriage. After a long and somewhat treacherous drive to deliver Phoebe to the care home where David has sent her, Caroline realizes that she cannot leave little Phoebe to be raised in this dark, unpleasant environment.