Hi there. I agree that that is a whole lot of stress and pressure you are dealing with on top of the grief from the passing of your friend and the ability to easily see your grandkids.
How in the world do I not let her and her meant to harm me comments not get to me?
This is where learning about and undersstanding the various behaviors and defense mechanisms come show up. Are you familiar with projection? It is a defense mechanism whereby the person with BPD (pwBPD) will put or project all their negative feelings or thoughts onto another person. When they do this, the pwBPD isn't even seeing you, they are just desperately trying to get rid of the negative. Regardless of how much it may seem like they are purposefully attacking you, under it all what she says and does is a reflection of what is going on inside of her.
Understanding that is what enabled me to not take it personally when my mother would say horrible things to me and accuse me of all sorts of things. I also used to use imagery when I was around her. I pictured a clear bubble around me and when she spoke I heard her words but they never actually touched me, they just bounced off. The whole time I was doing that, I would remind myself that she was really telling me about how she was feeling of thinking about her own self (ie, projecting). I think reading about projection and possibly doing something like the imagery might help you to not be so damaged by your conversations with her while you have so much going on and will need access to your father.
I am not suggesting these things as a way of being able to withstand verbal abuse. For me, it helped me to stay emotionally detached and allowed me to think of a response rather than reacting to her words. I was then able to say "stop speaking to me like that" or "I am leaving/hanging up now as I will not tolerate verbal abuse and you trying to press my buttons", etc. and then hung up or left. (and honestly, sometimes - okay, often - I lost my cool and yelled these things to her and used a few curse words but I did not care if it made her angry or give me even more grief. What I had been doing before was not working and certainly did not stop her so I opted to speak up and say no.)
How does that sound? Not the yelling and swearing part, but the other stuff? Be prepared though that once you start changing the way you interact with her, chances are she will ramp up the crappy and abusive behavior. This is called an extinction burst. Stay steady with your boundaries (refusing to ignore or put up with her pushing your buttons, etc) and over time, the frequency of the behaviors will often decrease. I mention that because a lot of people will say that boundaries do not work because the pwBPD will ramp up their abuse. BUT(!) how they respond does not matter because the boundaries are for you and your values and beliefs. Again, I am not sure I would do more than reminding myself that her hurtful words are not about you they are about her and the imagery (if that will work for you) until things calm down a bit.
Wishing peace to you and yours.