At this point I’m just going to go the NC route, work on moving on, and if she initiates and wants to have a conversation I’m willing to.
Probably the best option at the moment - you certainly can't make her do anything she doesn't want to do. Leave the ball in her court, at least for a while. Nothing wrong with sending her a brief 'hi, how you doing?' message after a while if you'd still like to keep the relationship going.
In the meantime, concentrate on yourself and your mental and physical well-being. We all know how thoroughly draining a BPD relationship can be. See friends, do hobbies and try to remember that you deserve a good life, not one of chaos and conflict. None of this is your fault, you were dealing with someone who sadly has a mental illness.
The 'Three C's' is often quoted here.. they are 'You didn't
Cause it, you can't
Control it and you can't
Cure it'. Be kind to yourself.
So, just because she was extremely cold, short and callous to me the last time we spoke doesn’t necessarily mean it’s final?
As I said, it might be final and it may not be. BPD's are capable of saying the most hurtful and cruel things in the heat of the moment and then can wipe them from their mind and deny ever having said them. Quite scary when you think of it.
This is how they can verbally rip you to pieces then next day smile and act as if nothing had happened - because in their minds, it didn't. Having said that though, I've always believed they are far more aware of their actions than they would have us believe. My exBPD would be really nasty when it was just the two of us but then instantly be nice if people came around - this shows a certain level of self-control and premeditation.
Without professional treatment though, BPD is a repeating cycle. Every time my ex came back there was the brief 'nice' period where I thought 'this time things will be different'.. but of course this didn't last and the chaos would start all over again.