Good question. Perhaps she was not as aware of her personal likes and dislikes as she should have been. That sounds like an addicted person saying, "I don't need this. I can stop anytime I want." Cherry Valance might not have been violent herself, but her actions speak louder than her words with regard to her likes and dislikes.
It could also fall into the stereotype of social expectations. Think of the star football player in a high school. Who would you AUTOMATICALLY assume he is dating? The head cheerleader. There are expectations with status that some people feel as though they have to blindly follow. You would be a little shocked to learn that your doctor was dating a Hell's Angel motorcycle gang member wouldn't you? You would expect a comparable profession just as in high school, you wouldn't expect a little rich girl dating some poor scum.
The "gang leaders" you mention all have something in common - they are strong and confidant. They stand tall with a determination that comes out of convictions. The convictions might not be beneficial or even legal, but the strength of those convictions make the men who have them come to life. Cherry is attracted to that strength.
Cherry, I think, also sees what is behind the curtain of confidence. She tells Ponyboy how Bob could be sweet sometimes, and how he would listen to her. Randy tells Ponyboy how Bob was really a good kid, but was always looking for someone to tell him no. We as readers know that Dally is a "good kid" at heart, and that Dally had a great capacity for love. Just as Cherry sees the beauty in Ponyboy's personality, I think she also sees the beauty in Bob and Dally's personalities, too.
This is a great question for the discussion board!
Attraction is a powerful thing LOL! In all seriousness, attraction IS very powerful. Opposites attract, and I believe this is one of the main reasons that Cherry is attracted to Dally. He is handsome and intelligent, but rough and a "bad boy." I think many people are attracted to people who are very different from them sometimes. Dally lived a completely different life than Cherry and this was attractive to both of them.
Maybe she was going for the "bad boys". She knows that Bob did bad things, such as beat up Johnny, so this may be the driving factor. I mean, c'mon, even though he had a little good in him, how can she overlook all the bad things and concentrate on the small amount of good, if that is what she likes about him?
Everybody loves "bad boys!"
maybe she thinks they are hoter and cooler than the rest of the socs and is afraid to be boyfriends with greasers. also she dosent seem to be very in love with bob seeing as see is a spy for the greasers and dosent really show that she is tramatized of his death instead she testifies for jhnoony and pony. i think that she hang out with bob just for urrm "street cred" or popularity