This teen needs to see a psychiatrist ASAP. You should talk encourage her to talk with her parents and teachers. Has she ever actually tried to hurt herself? Is she deteriorating to the point she cannot function? Is she living on the streets? If the answer to any of these questions is yes, then a person can legally fill out a form asking the police to take her to a hospital even against her will and a psychiatric exam will be done to determine if she needs hospitalization - involuntarily if she won't consent. This is called a petition for involuntary commitment. You can ask the police or the clerk of a court for this form and who to give it to.
A person cannot be diagnosed without a comprehensive in person exam. What someone says they say is not enough. A psychologist or psychiatrist will need to look at their body language, their affect and emotions, the way they talk and what they talk about, as well as their reliability (being honest about what they say). The examiner will need to talk to their family, friends, and physician to see what others see and hear and how the person has changed.
Ask her if she is willing to see a psychiatrist and then find out where the public mental health clinics are in your area. As she is a minor, she will have to seek her parent's assistance and permission for care. The parents must be informed. If the parents have health insurance, then they will need to go to one of the providers in their network. If there is no health insurance, she needs to go to a public health clinic. She can always go to the emergency room of a local hospital and ask for a mental health evaluation and assistance. Tell your concerns to the social worker at her school or a teacher. I presume you are also a teen. This is NOT something that a teen is able to handle on their own, either as the patient or as a friend of hers.
