In The Outsiders, what is Cherry's motivation for helping the greasers?
It is in Chapter 6 that Dally tells Ponyboy and Johnny that Cherry is acting as a "spy" for the greasers, and he goes on to explain to them why it is that Cherry feels she needs to help them in this particular way:
She said she felt that the whole mess was her fault, which it is, and that she'd keep up with what was coming off with the Socs in the rumble and would testify that the Socs were drunk and looking for a fight and that you fought back in self-defence.
However, as Ponyboy realises when he thinks about it for a little while, it was not "Cherry the Soc" who was helping them. In fact, Cherry is clearly so frustrated with the way in which you either have to be a Soc or a greaser and the way in which this is so damaging that she is moving beyond this particular identity. Cherry is acting as "Cherry the dreamer who watched sunsets and couldn't stand fights." Cherry is acting in a way to try and limit the violence and also do her bit to make amends for past violent acts that the Socs had committed against the greasers. Cherry is managing to do what Ponyboy eventually does, which is move beyond the distinctions of which particular group she is a part of and act in a way that shows her character rather than merely her tribal loyalties. This shows that she is a character to be admired and esteemed.