DCS,
I think you answered your own question..."I kinda feel like I'm being back burnered for something more important to her." You described her as a free spirit and flakey. You are probably into the excitement of living on the edge, but not really into her as a person. When you get tired of this relationship, I expect you will move on towards someone with more substance who has the time, affection and love to offer. It sounds like she is not ready for a long-term relationship, but is mostly interested in some short, fun adventures right now.
Blessings,
~ nmpb ~