You are right. Your friend is showing symptoms of a serious eating disorder. Although what you are describing looks like anorexia, I don’t have enough information to label it. But the label really doesn’t matter. What she has in common with those who are diagnosed is her unrealistic assessment of her body, her unwillingness to feed herself, and her exhaustion. The fact that she is now missing her period suggests to me that this has been going on much longer than the last few weeks.
Your friend is engaging in what could be life-threatening behavior. It’s already threatening her health. I truly wish there was a way to convince someone who doesn’t want to be convinced. Generally, arguing, debating, even presenting them with facts, doesn’t work. It’s not likely that showing her my response will help either, but it’s worth a try. I hope she will seek help knowing that I agree with you.
If not, I suggest you tell her that as much as you care for her, you are not equipped to help her. You could tell her if she won’t seek help herself, out of caring for her, you will be forced to let someone know who can help.
Your friend’s secret is not a secret you should keep. When people endanger their own life (or the lives of others), confidentiality rules are no longer relevant. If she gets drastically ill or dies, I don’t think you can or should have to live with the fact that you knew she was in danger and did nothing.
I’m sorry you don’t think her parents would be helpful. If that’s so, they probably won’t listen to you, a teen-aged friend of their daughter.
Your other option besides talking to her parents then, is to see your school’s nurse or a teacher you trust to clue them in. Her parents might listen to another adult, both because they respect adults more and, possibly, because they wouldn’t want the school to think they were not taking their daughter’s well-being seriously.
I’m very glad you wrote. Taking action could mean saving her life. No, I’m not being overly dramatic. A 2011 study that reviewed almost 50 years of researched showed that the mortality rate for people with anorexia is the highest of any mental disorder.
I wish you well,