Hi, Lucy Brown, and

I'm so sorry for all you and your family is going through! Things sound really tough, and I can understand your fears and stress. Do you have any type of help for this? Extended family? Friends? A Therapist? Do your parents have any type of help available to them?
One of the first things that might be wise for you to do is make a Safety Plan if you don't have one already. This link has information that can help with that:
Safety First. Another link that can help you with navigating your way with your sister is this:
The Do's and Don'ts for a BP relationship.
Have you had the chance to check out the
Workshops and
Articles on this site? You can check out those links and find the subjects that are most helpful to you. Your situation sounds terrible and serious, and I hope you keep yourself safe... .Please keep telling your story and asking your questions, and read all you can around here; it really will help