I am so sorry to hear what happened to your sister. Even at my age, I still can't believe how cruel people can be to each other. Whoever did that to your sister is nothing more than a low life animal.
But as others have said, you need to be stronger now than ever before. For yourself and your sister. I've heard so many stories at AA meetings where people had to face terrible tragedies or losses, and were so happy to be sober so they could be there when they were needed. The last thing you want is to not be sober. Take care of yourself. John