Cherry does not really appear very much in these last chapter, but she still has a pretty important role. I think her role in these chapters is similar to her role in the book as a whole. She is the person who is helping to bring the Socs and the greasers together. She is an influence for good in the book and these chapters.
In the last couple chapters, she shows up or is referred to twice. Once, Pony thinks of her and that makes him think more about how Bob might not have been such a bad person. The other time, she gives honest testimony at the hearing about Bob's death. In both cases, she is helping to create a situation where the Socs and the greasers can see each other as real people.