Self injury is a means that some people use to express or release emotional pain. This may include carving, scratching on the arm or leg, superficial cuts, cigarette burns, pulling out the hair, or picking at their skin. It is important for your sister to express her feelings openly with a person that she feels safe with--often this is a counselor or therapist especially in more serious cases. In less severe cases, journaling or other more positive ways of coping with intense feelings can be a helpful way to work through the emotions that are causing her to self harm. If your sister is self injuring it is important to get someone (like your parents) involved who can help her and provide support.
You're right in really being scared for her and loving her. But not right for not telling your parents. If your parents care about you two then they will do their best to take care of the situation in a good manner. I used to have this problem when I was younger and spent some time in a hospital getting better. If my mom did not help me through that I probably would not have gotten to where I am today. Parents may be scary or upsetting at times but good parents really do want what is best for their children. This means making sure they are safe from harm and pain, both mentally and physically. Telling your parents is the best way to go about it, and they will be able to find somewhere that can help her with the issues she may be battling and she will get better. Always be sure to be there for her. She needs someone in her life at such a rough time.
She will kill you for this, but tell your parents. Mine went hysterical too. I would have stopped a lot sooner and not gotten addicted if someone had the balls to tell my parents. My brother thought I wouldn't do it anymore because I promised him. Just like any other addiction we lie and manipulate so we can keep at it.
Tell your parents and then help her deal with the aftermath. Stay on her side but tell them.
My sister is cutting right know and im scared too. what you need to do is tell a parent right away cause it can get out of hand. My sister is saying she will kill herself if I tell my dad. But you need to tell an adult that you trust right away!!!
Good Luck with you and you sister!