How does the author use foreshadowing in A Storm of Swords?

In Chapter 15, When Robb Stark forgives Catelyn for her release of Jaime Lannister, she is relieved that he can be so understanding. He says that people cannot help what they do for love, and she feels like he understands her reasoning. However, he is foreshadowing his own admission that he has married Jeyne Westerling when he was supposed to be marrying a Frey woman.