Don't drink. The one thing drinking does dependably is make things worse.
My heart broke for your sister (and you) reading this. This happened to a member of my extended family about 18 months ago. A nightmare.
With the support of family, friends and services for survivors, she remains the vibrant and lovely young woman she always has been. No assault can take that away from her.
My thoughts are with you and your sister as the rebuilding process begins.