DSM--- I feel I could've been the author of nearly the same letter 3-4 years ago. The advice to end this relationship is spot on. Your future ex-partner may or may not be fine afterwards. I hope she truly is someone who just needs to be on her own to find her own thing. From your letter her version of adulthood doesn't really sound like it's in such a bad place at the present except for the part where you're deeply unhappy with her and she with you. I suspect you'll find that when she's gone you'll discover as I did that the narcissism and feeling of lack of control (and it really is about control and security, generally) in your life won't get any better without her. It could be that what you'll find is that the feelings about her that have frustrated you, and it does seem like a miserable situation, will now reveal themselves as free-floating aspects of your basic condition at this time in life. In my case I had to do some serious work on a problem that began early in life with my mother inappropriately using me as an emotional support. Emotionally, people in my life lived all over me. I in turn have done the same and have been attracted to the same. Finishing with her while necessary won't solve your existential problem, whatever its specifics, but it's time to get on with meeting the challenge of your life head-on without the distraction of another fully capable person's own problems to distract you and give you meaning.