Everyone needs a best friend. For Deborah, that friend is Carla Stoneham. In fact, Carla is the first true friend that Deborah has since since she was very young.
Carla lives at the mental hospital with Deborah. She lost it after her mother killed her siblings and then herself. She shot Carla, too, but Carla survived. We'd be pretty messed up if that happened to us, too.
Deborah and Carla are honest with one another about their fears, their symptoms, and their hopes for functioning in the world outside the hospital. It's that honesty that glues them together—and that helps them get better.
At one point, the girls leave the hospital together, run in the rain, and come back well after midnight after walking through the neighboring town. They've violated the hospital rules, and they feel good about it. They've conspired to have fun together, and that's a rare thing in this setting. The event cements the bond that they share.
Carla eventually leaves the hospital and rents a room and gets a job. She sets an example for Deborah that getting well and existing in the real world are real possibilities.
We all need that one friend who sets a good example and has our back.