I can understand it's confusing to try to make sense of her behavior. You may never get the answers from her as to why she's so inconsistent. Regardless of what the reasons are, her inconsistent behavior and perceived lack of interest in the friendship is enough reason to scale back on reaching out to her....especially since you tried bringing this issue to her attention, and she failed to attempt to make changes.

It would likely be healthier to begin to shift your focus on to others who are for most part, consistent and show more interest in the friendship. If your friend makes changes, it is up to her to show you through her actions. Since she hasn't after all this time, it's probably best to just move on, let her reach out if she finds the friendship worth sustaining, and turn your attention elsewhere. Just my two cents.