Please help....******HUGE SPOILER*************

The scene where Libby tries to give Theron a ride home from work is when she was planning on telling Theron she was pregnant with his child. As she mentioned, it had been six weeks since they had seen each other, just enough time to notice the baby and get tested. She backs out after Theron talks about the hatred between his parents and how he planned on never making the same mistakes. So she doesn't want to trap him, but that puts her in a terrible situation, and Rafe marries her to save her from scandal. She clearly isn't that fast of a woman, just look how long Rafe and Libby wait before getting physical. They were legally married, yet neither of them took advantage. That they both preferred to wait for real love to bloom says a lot.

It is important to the film's themes to understand that Theron found himself making the same mistakes he had grown to hate his father for. He allowed his son to remain legitimate by society's standards, and for the same motives of saving certain loved-ones from scandal. That is why he forgives Wade at the end, and why he passionately runs after Wade's killer. It is only some bitter irony that the child being fathered by Theron meant it resembled a child of Wade's. This triggers the death of Wade, and cements the villain of the story, being the gossip and scandal that controls all the characters in the story.