Hi Suki,
I’m sorry to hear about your situation, that is tough!
One thing that has helped me deal with the people in my life that have bpd is to focus on myself and the things that I can control. In your case, you probably can’t force a change in your sister’s behaviors but you can control how to respond to them.
If there is physical abuse happening, that should not be tolerated and you need to ensure your own safety.
The “tools” section on the site has a lot of good articles that can help you. I especially found the one about setting boundaries to be helpful:
https://bpdfamily.com/content/setting-boundaries
