Hello jazz5579, deepest condolences to you on your mother's passing. You deserve a hug. Also, I'm sorry to hear about the difficulties you're facing with your sister that have brought you to our community, but glad that you found us, so a warm welcome to you.
I can only imagine how hard it is to handle your sister's behavior at what is normally an extremely difficult time for everybody. It can't be easy and is taking it's toll on you. Has your sister been officially diagnosed with BPD? How old is she and does she live with you? It sounds like you have to take care of a lot of her needs such as grocery shopping?
When a family member has BPD, the illness can negatively everyone in the family system, and it sounds like you and your brother are bearing the brunt of it from what you wrote. Community members on the
Coping and Healing from a BPD Parent, Sibling, or Inlaw board are experienced with and can help you with setting boundaries and improving your handling of relationships impacted by your BPD sister. You can find a lot of information and support that can help you with the journey in front of you.
Once again, my condolences to you on your mother's passing. I hope you keep reading and posting here as much as you need, there are so many understanding and supportive people. I know that it has been a godsend for dealing with the pwBPD in my life. I hope that you find the help and support you need at this difficult time. Best wishes to you!