This statement reveals that Cherry is secretative trying to keep her association with Ponyboy and the other Greasers a secret from her parents. It is a reflection of the divide between the Greasers and the Socs that Cherry must keep hidden, a divide that is further highlighted by the fact that Cherry and Ponyboy come from different social classes.
Cherry's statement also serves to highlight the strong sense of loyalty and solidarity that the Greaser gang has. Despite coming from different social backgrounds, Cherry is still willing to stand with the Greasers and protect them from the judgment of her parents.
Hope this helps! Have a great day. :)