Your friend has bulimia nervosa. You can read about this disorder at www.rebeccashouse.org/more_information.asp. This can be a life threatening disorder. First your friend needs medical attention. Encourage her to be honest with the doctor, so they will know what to check for. Depending on the severity she may need stabilization at a hospital or an inpatient eating disorder treatment program. If she is stable, she may be able to attend an outpatient program or work with a therapist who specializes in eating disorders along with a registered dietitian. You can not make her recover. This is a complex disorder, but you can give her the information and let her know that you care and will support her in her recovery.