As gently as I can, I would encourage you to see a psychologist who specializes in eating disorders about your bulimia and self-mutilation. You need to talk to someone about how you feel about yourself and find a healthier path in life. Food is not the issue and I would really hope that you find a therapist to talk to about your issues.
The text I used in the Healthy Body Calculator® are rather gentle and it doesn’t use the words obese and definitely not “fat ass”. The calculator is designed for adults, not teens. If you want to send me your height, weight, and age, I will give you some feedback using the Healthy Kid Calculator® if you are receptive. Also, ask your friend to send me the data she entered so I can try to reproduce her results.