It must be really frustrating to see someone you care about hurting themselves.  All of the things you mentioned that she is doing are self-destructive.  Young people often engage in these types of behaviors because they want to feel better.  They want to escape the emotional pain they are in. Sometimes they do it to fit in to a peer group that thinks these behaviors are cool.
 
Do you know if there is something causing her emotional pain?  Will she talk to you about what is stressful in her life?  Sometimes it is school, sometimes relationships, and sometimes it is unrealistic expectations that she is putting on herself.
 
There are actually two things that you can do to help her.  First of all encourage her to talk to you or to someone that she can trust with her feelings.
 
Secondly, let your parents know that you are worried about your sister and ask that they join you in helping her.  They are actually in the best position to get her the help she needs. Initially your sister may be upset that you shared information about her with your parents.  You are doing it to help not to hurt her.  Some day she will thank you.
 
Boys Town National Hotline
1-800-448-3000