Given scene/plot descriptions from movies or TV shows, and given a specific question about the scene, summarize the question into a title

In Season 3 Episode 6 Sansa is dragged all across the story, for who she's supposed to marry. I don't quite understand why she's so important. Because there is her brother Rob, who is the King of the North and Lord of Winterfell. And if he fell wouldn't all of that go to Bran (although he may or may not be alive according to their knowledge)?
Why is Sansa Stark so important?