Because she wants to escape from the sheriff, and Nevada is outside his jurisdiction. While it's good to know your motivation for including the action, that's not sufficient. The reader has to believe that this character has her own reason for taking this action. Success is a pro-active motivation because it draws the character forward towards itself. Motivating movement AWAY from something.
Guilt is a reactive motivation because it propels the person away from itself.
This affects the trajectory of the plot. Most motivations have both a negative and a positive aspect. Internal motivations are what will individualize your character. Story is the actual action of the book. Give the character something immediate to inspire action today.