Obviously the situation has many different variables and is not simple to understand, but my reading of the situation from afar has me sensing that she is perhaps deliberately manipulating (not in a bad way, so maybe a better word might be changing) her social situations and her behavior in those situations in a experiment to see what happens when you mix different variables.
Is it a result of the looming college scene and her entry into a more grown-up world? Probably, in some ways. Perhaps she's at a point where she is actually solidifying and accepting who she is, and verifying her actual identity by trying out others just to rule them out. My guess is that, being as smart as she is, she has always been a very analytical person, and she is now applying this trait to testing out her social identity.
I completely understand why you're worried. She is not a cookie-cutter kid and her life beyond high school is looming for you, too. She probably doesn't fit in as completely herself anyway, anywhere. But then again - and maybe most importantly - none of us truly do. We all modify ourselves to fit into whatever situation we are in. She just has a bigger mismatch to account for, and she's 14. So, I suspect most of it is typical teenage angst, but on a bigger scale. And perhaps she's questioning who will be there for her as she moves into new territory as she approaches monumental life changes that come with the end of high school.
FWIW, your DD seems to me to be very self-aware and, while she feels tremendous anxiety about some things, I think it's a good sign that she is aware of it. And, even though she doesn't always want to figure it out with you (and what teenager wants to, honestly) it sounds to me like she knows you are there for her and will be there for her no matter what.
