Hi Jacqui,
Welcome and hello
I'm sorry for what brings you here, and at the same time glad you found the site.
I am learning to coach my BPD loved one instead of rescue and fix, which is a hard transition to make for me.
With you D, I wonder if she might have some OCD traits to help explain the spider phobia. Any idea why this phobia recently developed for her?
You may be able to work with her son and coach him to competence so that he feels empowered. Is that possible? Showing him what you do when you see a spider, model for him how to remain calm, admire him for handling it himself, and then when it happens again, recognizing and acknowledging his competence. I don't know why I think it might work best to do this with him and not your D. I guess because fear of insects can be a very fight/flight fear that is hard to change. Giving your grandson the skills to handle the emergency will help him learn BPD skills and regulating his own emotions, while also showing you have confidence in him, and that leads to a feeling of competence.
I also found that validating questions are among the most powerful for me in my skill box. This places the responsibility for the problem where it belongs while also being supportive. If I am overly competent, I tend to trigger or foster victim behavior, which can then turn to resentment that I have no confidence in her abilities.
Because pwBPD tend to externalize emotions, how we respond can have a powerful impact.
LnL