I'm replying to myself, but I'll have you know, East, that I spent my walk to work thinking about this, and I would like to take you by the shoulders and shake you a little bit.
One thing I neglected to point out to you on the topic of healthy boundaries is something you should be paying attention to: You set a boundary by ending the relationship. She is fighting you on setting that boundary. That is not respectful behavior. That is not respecting your autonomy.
An emotionally healthy woman - if she dated you in the first place - would say "You know, I'm disappointed because I really like you, but I know I took a risk by dating you before you were really ready. I wish you the best!" and move on to heal and find someone emotionally available to her.
An emotionally healthy woman would respect your decision to break up with her. She'd know it takes two people to create and stay in a relationship, and just one to end it.
The one you're actually dealing with is trying to tell you that you are wrong, and she knows you better than yourself. She wants to fix you and earn your love to prove her worth to herself. She wants you to reverse the boundary that you have every right to set because SHE is scared to be alone with HERSELF. Not because she likes you so much, but because she's made you into a barometer of her worth.
East, this has Absolute Disaster written all over it. You are both insecure and codependent but neither of you can see through your emotional pain enough to notice. Limit the damage to the present. Set the boundary and notice it that she isn't respecting it. Her actions are very telling of her character.
