Let me start by answering the final question in a more concrete way. The reason that the reader is experiencing Dana's journey in lockstep with her is because the narrative point of view is first person. What Dana experiences, we experience. What she feels and thinks is what we experience, and what she learns, hopefully we learn. I believe that is the larger question here. Why is it important that Dana and the reader experience what we experience? The answer to that question is much more subjective and best left up to individual readers.

What Dana experiences back in time is horrible, and it is tough for her and us to know that she can't do anything about it. I think that is an important message for readers. You can't change the past, but that doesn't make it any less important. It's important to know your past and where you came from in order to better understand where you are now. That is a valuable lesson that Dana learns from her experiences, and readers hopefully learn it too.