I think it's how far she can go back. Information obtained from 5mins ago won't affect the future that much but information obtained a few hours ago can causing her to jump or more specifically, the point of change take on a different route. To balance this powerful ability, the world requires something in exchange. Like an exchange for the defeat of Draken is worth something like turning Ziggy evil and awakening him from his slumber.
All I'm saying is that the higher the impact of change she wants to create to the world, the bigger the negative effects the world has create to balance it out.