When Cherry tells Ponyboy, "We couldn't let our parents see us with you at all," she is demonstrating the trait of social conformity.
Social conformity refers to the tendency of individuals to adjust their behavior, attitudes, and beliefs to align with those of the people around them. In this case, Cherry is conforming to the expectations of her social group, which includes her parents, who likely hold negative attitudes towards Ponyboy and his group of friends, the Greasers.
Cherry's statement suggests that she values her social status and the approval of her parents more than her friendship with Ponyboy and the Greasers. She may be worried about being judged or ostracized by her social group if she associates with the Greasers, which motivates her to conform to their expectations