What is the novel rules by Cynthia lord main conflict?

a new girl moves in next door, and catherine has to try hard to not be herself when she's with her. meanwhile, she meets a boy who cant talk or walk when her autistic brother David has to go to OT,or occupational thearapy. kristi,the girl next door, begs catherine to ask jason,the boy she meets, to the dance. meeting these new people and doing new things flips her world upside down, leaving her torn:what's real, and which is the right way to go?