So much of Franny's early years were kept from her. She doesn't remember her father or understand why she and her mother left Australia. But at her young age, Franny sensed that she was different- -that she didn't belong. She explored and roamed in a search to find herself. "I wandered along those curving walls...I knew they must lead to the place from where I truly came." Her difference was reinforced- -and not in a good way after her mother left her- -blaming Franny before it even happened.
I think most of all it is a part of who she is. (Her grandmother wandered, her mother...) Some people are restless and need space and distance. I think back to many trips I have taken and how I have wished, oh how I have wished that they did not have an end--that I could keep moving to see more of what is out there, to feel free and unencumbered. A journey is an opportunity to escape one's "real life" and responsibilities for awhile. A journey is an opportunity to detach and refocus so that we can be more present once we return.
What if there was nothing wrong with Franny's roaming? What if it really was inherent to who she was? What if it was a part of her that no one had ever understood or accepted until Niall? We like to attach labels to people who don't follow accepted norms and search for reasons to explain their behavior. Maybe that just isn't necessary. I admire her for doing what come natural to her instead of doing what society told her she was supposed to do.
(I am not denying that she has unresolved issues and suffers the affects of childhood trauma. I don't think they are the primary reasons for her leaving.)