She's Hurting Herself - Help

There are different reasons why someone may be intentionally hurting themselves. The most common reason is that experiencing this type of physical pain is a way to deal with and temporarily experience something rather than emotional pain. Another reason can be to get attention and to control people in a relationship (in this case to keep you and other friends attached and concerned). In other cases, but not likely in this case, people will hurt themselves to try and "disfigure" themselves to become less attractive to protect themselves from certain types of attention.

There are a number of underlying mental conditions that could be involved. The bottom line, regardless of what your friend is trying to do or the underlying cause, is that your friend needs help. The best thing you can do is help your friend get help from a qualified mental health professional in your community. You may be able to do this on your own. In honoring your promise, are there other concerned adults in both of your lives (bests parents or teachers) that you can turn to for help. You might think of religious leaders, activity leaders, counselors, etc. If there is no one else and your friend is unwilling to seek help, you may need to tell them that this is serious enough that you can't honor the promise.