How do you guys tell your story?
Exactly like you just did dunc, one post at a time, as we grieve, learn, grow and detach.
The only way I could explain what happened is that my ex with BPD was a succubus, a siren, who was so damaged she was running low on some mythical 'life force'. She latched on to me, and over the relationship drained me of mine in order to keep herself going (this is true to an extent, I paid for her to live so she could study for her Masters Degree, whilst I worked any job to pay the bills). When she had finally drained me of my energy, my soul, I became so fatigued emotionally and physically she could sense this - so devalued, discarded and left me quite simply as an empty husk and went out (and quickly found) the next vessel full to the brim that she could drain.
It's helpful to not view our exes as mythical creatures, and she didn't "latch onto" you, she attached. A borderline does not have a fully formed self of their own, because they didn't successfully detach from their primary caregivers in infancy and develop their own self, so attaching to someone else to "complete" themselves, their self, is mandatory. And when you showed up as emotionally and physically fatigued, she may have felt impending abandonment, you were losing it and she knew it, and abandonment is the worst thing that can happen for a borderline, so she left in search of a new attachment. Not malicious necessarily, it's just a reaction to emotions a borderline can't soothe on her own, but folks with personality disorders don't think like those without one, and have an entirely different set of priorities.
It's great that you have a friend who would spend all weekend with you. And it's also important to take care of yourself very well right now, eat right, sleep enough, get a little exercise, keep talking, and identify any self-defeating copying tools you may use at times like this. Take care of you!