In The Outsiders, why doesn't Cherry want to see Dally again?

In this novel by S. E. Hinton, two different social groups of adolescents are at odds with one another: The Socs, who come from wealthy families, do well in school and are expected to become productive, influential members of society; and the Greasers, from poorer families, who don't have strong family role models and who tend to be rebellious and do poorly in school. Cherry is with the Greasers, Dally or Dallas is with the Socs. When the two meet there is immediate tension and Dallas flirts with her, while Cherry is rude and insulting. To complicate matters, Dally's younger friend Ponyboy has a crush on Cherry.
In the film version by Francis Ford Coppola, Dally is played by Matt Dillon and Cherry by Diane Lane. In the scene being discussed, Cherry yells at Dally and he mocks being offended, but seems to know that she likes him. After Dally walks off, and Cherry is standing with Ponyboy, she states firmly, "I hope I never see Dallas Winston again!" After a pause she roll her eyes and says more softly, with a frustrated air, "If I do, I'll probably fall in love with him." She walks off, and Ponyboy looks dejected. This dialogue is slightly changed from the book (Cherry says  "I could fall in love with Dallas Winston... I hope I never see him again, or I will.", but even more effective.
Dally and Cherry come from different worlds, but there is a sense of the forbidden in their attraction to one another. Dally is more reckless and exploits this attraction by flirting; Cherry is more hesitant even though it's clear she is interested in him.