Ex with untreated BPD giving me weird signals. Don't know what to do.

[XenonElement54]

Hello everyone,
I am new here and I have been facing an interesting dilemma the past month or so that I could use some advice on. About a month ago, my ex (who I'm 99.99% sure has quiet BPD) discarded me in a flash. One week she was talking to people about where we were gonna move in together, the next she was breaking up with me. It was extremely jarring and I didn't know how to take it, but now that I've done more research, talked to two therapists about it, and read some books, I am now fully convinced that she has untreated BPD. Only problem is, we have a TON of mutual friends, and also live in a small town, so it's difficult to avoid her unless I just cut all of those friends out of my life. I didn't want to do that so I still occasionally see her. It's not as hard as it used to be to see her, but she keeps talking to me and wanting to be friends. I told her we could be cordial and not be friends, but just if we see each other, I can handle saying hi or whatever.
Fast forward another couple of weeks and I see her at this running club I go to. She says hi, does some small talk to me or whatever and I just answer cordially like I said I would. We start running and she's purposefully keeping pace with me (she's WAY faster than I am), and talking about all kinds of stuff trying to start up conversation with me the whole time. I didn't really know what else to do except just talk back, cause we were stuck out on the trail. The run ended and then she tries to talk to me again. What is going on? Literally not even that long ago we were both invited to a party (that neither of us knew we were coming) and she left early because I was there (she texted me to tell me that). Now she wants to try and be friends or something? I have no idea.
I am setting firm boundaries with her, I told her that I did not want her back and that this would simply stay as cordial. Not friends. What do ya'll think I should do?

[LaRonge]

It sounds like you're doing what you can do. Since you have similar friends and live in a small place, it seems unrealistic to try to cut all those aspects out of your life just to avoid her. I think setting boundaries is right, and since on her part her behavior is to feel less bad about herself and get your attention, she will eventually get bored and move onto someone else. Focus on yourself and keep her at a distance, but don't change your life entirely because of her. That's my two cents.