OK, I think I've come to a conclusion.

Yes, it sucks that after having put so much into the relationship, it ended the way it did. Whether she had a personality disorder or not (and I honestly don't know if she did or didn't), we both had different outlooks on life and our differences would probably have meant that things would have broken down at some point anyway. As for maintaining some kind of friendship, she clearly doesn't want that. Not really much I can do about that, however much it sucks. I guess she has her reasons. I still wish we could have parted on good terms and discussed things to get some closure, especially after everything we shared together. That really is the worst part of all of this for me, because I'd really have liked to have understood why it had to be this way. Even if a relationship has to end, for whatever reason, that doesn't mean you can't end it in a good way... unless someone did something REALLY bad that's unforgivable. Having said all that... at least this has allowed me to see how a relationship can turn someone who was previously more or less independent, into an anxious, clingy, needy, desperate, dependent, pretty much obsessed, person. That's not who I am as a person at all. And although I can understand how our different personalities could have contributed to that, I shouldn't have let it get to that point. Like others have said previously, working on self-esteem, boundaries and such should help prevent something like this happening again.

Summary - Relationships sometimes don't work out, and that's OK. Some people aren't a good match for one another, and that's OK too. If you find yourself having to sacrifice things that are important to you in order to try make a relationship work, that's probably a sign it's not right. I have a pretty good brain, and I shouldn't have gone against what it was telling me.

End of thread! Thank you all!