Character Analysis
It doesn't take long for us to realize that Bailey is a lot like Tibby—after all, these two are both about as sarcastic and cynical as they come, or so it appears anyway. Upon closer look though, Bailey is much smarter than Tibby, and possesses a whole lot of wisdom about life, perhaps because she's facing death.
Initially Bailey seems like a girl with a chip on her shoulder, and why shouldn't she? She is twelve-years-old and battling leukemia; her body is frail and tiny, and she swims in the Pants when she tries them on. Her "thin, almost transparent skin" looks "bruised and blue around her eyes" (14.24)—so while the disease doesn't seem to be hurting her spirit, it definitely has taken its toll on her body.
Bailey instantly feels a connection with Tibby and wants to share in her life. She admires Tibby and wants to be like her, so much so that she shows up at Wallman's "wearing cargo pants almost identical to the ones Tibby had worn the day before" (9.14). Tibby's tough exterior doesn't scare Bailey off, and she persists in trying to form a friendship with Tibby, and eventually becomes co-creator of the suckumentary. These two enter each other's lives at the perfect time—they both need a friend to help them survive the summer.
Unfortunately Bailey's version of survival is quite literal, and as the summer progresses, her health deteriorates. Her one wish is that time doesn't run out before her true self is revealed, since she is afraid people will make "quick judgments and mistakes" (14.27) about her, just like Tibby does. Knowing full well how much flash decisions about people can hurt, Bailey bugs Tibby on the regular about her propensity to do just that.
Ultimately, Bailey's role in the novel is to show Tibby how to live life in a big way. She teaches Tibby that most people are worth knowing, and that it's important to be there for those you love. She may be young, and she might die, but she makes a big—and lasting—impact on Tibby's life.