Loners

I'm behind on all my acronyms.

This relationship does sound kind of complicated....She sounds "unreliable" or "changeable" in regard to her feelings or attitude toward you, and that would bother me as well. One thing in particular stood out for me, and that's where you said she's been nice to you, taken you on trips, etc., but that sometimes she's "mean and rude"..Hmmm..I'm just curious, but have you ever called her out on that behavior?..I ask because I had friends like that throughout my life and at certain points I felt like I was taking too much crap and finally called them on it..I lost a couple of supposed "friends" like that, but felt much better about myself demanding basic respect. Those who were truly friends did NOT leave and we were able to work it out.
Whatever you do, please don't view her behavior as an indication of YOUR worth. Rather than wondering if you're a person who thinks you're closer to people than you really are, maybe you should consider the possibility that you didn't really know her as well as you thought you did...It happens to people ALL the time, hence the oft asked question "Do we ever really know people"?
Take care, and be kind to yourself.