It's not your job to fix her. It's your job to love and support her to the best of your abilities, which it sounds like you are. It hurts so much not to be able to save people we care about. However I believe you are doing exactly what you should be. You've helped her access a safe space and professional help. Shes not alone. What a wonderful sister you are. Please dont be so hard on yourself and I hope your sister gets what she needs. Hugs.