Sarah, the symptoms you describe resemble bipolar illness, frankly, but we aren't doctors, so we can't diagnose. Things that appear to make it seem as though it might be a form of bipolar illness are the cutting, the overdosing, the anger, the silent treatment, and worsening of symptoms.

In my view, Sarah, you should encourage your friend to see the family doctor and request a referral to see a psychiatrist for help. Even if that person is not bipolar, she has issues that need to be corrected. She may have a chemical imbalance that needs to be corrected with medication.

If it is bipolar illness, it can get worse untreated as the years progress. She needs
help and she needs to be stabilized. I encourage you to do everything you know to
do to get her in to talk to a psychiatrist (or family doctor for referral to a psychiatrist).

Good wishes to you.