Welcome Me-Time
I can't believe I fell for it, my whole world was a lie for so long, how could I give up so much of myself for this person, sorrow for her lonely existence that will be her life forever, etc.
There are thousands of us here who "fell for it", BPD is a very serious mental illness and the mirroring stage is absolute nirvana for so many. What seems like a lie was really a disorder running its course, with very different realities for you and your ex.
Keep reading and learning about BPD, posting, and when you have learned enough about why your ex. did what she did, shift the focus to why you stayed and tried to make it work.
I know how painful it is to finally give up hope for it working out, you're right in saying you need to heal, and you're among friends here who can help.