I've met my uBPDxso the day before yesterday as part of a planned get together of a group of friends for a race we planned to run together. She originally invited me a few months ago to join and run together, and we even me a couple times to practice but the turn of events was that she flipped and split me black a couple months ago after a beautiful half day we spent together with her son and his gf (on Valentines Day of all days).
I was strongly advised (here and by other friends) to skip it and prevent the trigger as previously these kind of contacts crushed me as I always ended up with unrealistic expectations to get close again and facing the harsh reality of BPD pull/push soon after.
The discussions on this board and the advices I got here really helped me to better understand her BPD traits and myself with my codependency and obsessive/addictive traits and the circumstances that lead me to where I am today.
During the days leading to our meeting she flipped back and forth about being there and after saying she is not, she changed her mind and asked us (her old friends) if she can come with 3 other (new) friends from her new town that she has moved to recently. It pissed me off, especially as she said they are not sure that they will stay over and they need a place to sleep just as an option. I know I'm probably over sensitive but being just an option for an ex significant person in your life is not what I want... .
Eventually I decided to go because a. I wasn't terrified by it (unlike previous encounters) and b. I wanted to face her and my empotions about her and c. I wanted my friends to see how she behaves in front of me in their own eyes so they will better understand.
The meeting was just as expected. She was very distant, cold, and not very communicative with me. I was as friendly, nice, and warm as I always am and although she did respond, she did not initiate any contact with me the whole evening as if I didn't exist.
We stayed over in this 4 br apartment and I couldn't get a minute of sleep. I was over-excited by the fact she slept in the next room (with a female new friend) and hearing her voice, smelling her, and just being in her presence still make my heart pound like crazy... . I mindfully examined how I felt in these moments and calmed myself down so I was at least able to get some rest.
She want out for the race an how before me. It was so odd to hear her getting ready with he new friends. It reminded me the virtual reality she's living in. Instantly friends and so charming with people she really doesn't know, and so cold and distant from close friends who actually love and appreciate her (like poor me... . ). I sensed she is manic again and the excitement of moving and making new friends is overwhelming her - but I kept reminding myself that's she is not the point. I came there to focus on ME and on getting better and detached from her.
After the race, I finished earlier and I knew that if I stay we'll see each other again and I really wasn't sure I wanted that. Most everybody who saw me and know us asked about her as we were running partners for the last 3 years or so and it was an additional straw on my back and I decided that I really don't want to see her the way she behaves to me right now. This hurts. This is toxic. This is causing me pain. She wants no contact and she seems to not care at all about me and about my life and that's OK and I respect that. And I need to move on, regardless of how I feel for her. A working r/s must be mutual. Trivial but important to internalize

I took off. And that felt SO GOOD. Real freedom of choice. It felt like breaking from unseen emotional chains that tie me to her as I finally put my own well being in higher priority than caring for her.
PS. I asked one of our mutual friend how her run was as it was a first for her (milage wise) and I was concerned. So it went well (and I am proud of her, don't get me wrong) and she was very emotional when she finished it - burst into tears and was very happy about it. And he also told me that she asked him about me and how my run was and generally how I am... .
So:
a. I am still very glad I took off. This is definitely the right thing to do.
b. I am glad she hasn't forgot about me and she still cares about me, although she wants NC.
c. I feel calmer than ever before in the year or so.
PS2, on my way back I stopped over to meet a girl I met recently (she's also a runner) who invited me for a drink. We had a great time together, got closer, both emotionally and physically, and it is moving in the right direction. I'm optimistic that this could turn into a more serious r/s; my heart feels more open for a new r/s right now.