Suddenly, after an unprovoked angry toned message she has virtually cut me off and has been responding to messages with one word answers if at all. I have informed myself extensively about BPD , but being a sensitive person I'm finding it really hard ... just not coping, & feel that my own mental health is really suffering.
Sometimes when people with BPD traits feel bad, they try to shift some of those bad feelings on others - essentially making you feel bad makes them feel a little better. Its a dysfunctional way of coping, but not uncommon. In a sense, you having it together is upsets her because she doesn't have it together, so she levels the playing field.
My ex blew up a milestone birthday party and confessed later because it wasn't fair that I should be so happy. I really didn't get that at the time, but do now. At the time, I was devastated ,just as you are.
The best thing is to see it for what it is and give her space. Don't retaliate or be coy, just work with what she gives you and let her take the lead.
You: Wow its a beautiful day! I'm taking my dog to the park and then going to lunch. Want to join us? What are you up to?
Her: Nothing.
You: Are you OK?
Her (two hours later): Yep.
How should you respond to this type of thing?
Try to "read the room" and experiment to see what works and what doesn't work. One response might be,
are you sure? (open ended). Another might be "OK" (close ended). If the first doesn't work, try the second next time.
Next time you contact her you might want to use open probes to see if she engages.
What are you up to? If she talks, great. If she gives you a one word answer, give her a similar neutral response.
You: What are you up to?
Her: Nothing
You: Me too.
You: What are you up to?
Her: Well, blah, blah blah
You: Me too. Why do you think...