Hi Estelithil,
Glad that you've popped back in to visit us. First let me say that I'm very sorry about the loss of your grandfather. How are you doing with this? It is never easy to walk through losing someone that we care about.
I'm also sorry for your mom to have lost both of her parents within a few years. The same thing happened to me as I lost my uBPDm in 2012, and then my father in 2015. While I do not have a PD, I can say that I have a bit of experience in dealing with the loss of a parent. I'm a bit younger than your mom, but not much.
Mum is only 58 but since pop died, she's been acting like she has dementia. I suspect she wants her three daughters to gather around her and make her the focus of our attention - my sisters agree but we are all worried about what to do.
These past few months I've been attending a grief group to help me in processing my losses. I think I can understand how your mom is acting like she has dementia. Grief affects everyone differently, but we know there are some similarities. Those include feeling like you are walking in a fog, you can't think clearly, loss of focus, terrible forgetfulness, extreme fatigue, depression, and on the list can go. I think a better description of the feeling of walking in a fog would be that it feels as if you are walking through mud almost knee deep, and each step you take pulls and sucks at the boots you are wearing. Eventually you get so tired from the effort that you nearly give up, and your boots get sucked off and stuck in the mud. I've learned that it is common for a person to take 1 to 2 years to grieve over a loss such as your mom has gone through.
What type of dementia like symptoms are you seeing in your mom? Does it sound like any of the ones I mentioned? It is evident that you are all caring of her, in spite of her BPD behavior.

You really do face a challenge in sorting out what is grief and what is BPD. Are you all able to split up some of the caring of her so that the burden doesn't fall on any one person?
And most important of all, how are you caring for yourself?
Wools