Is there a safe way to become a really thin person?

Excercise, good food. You need first to determine your ideal weight, closely tied to your height if you are truly overweight, counting calories and regular aerobic excercise is the safe way to get where you shoud want to be.
Diet and exercise. The goal is not to become thin, but to become healthy. Diet and exercise is the best choice. If your goal is thin then you may need some counseling. Women are constantly being pressured to get thin. Bony is not sexy or pretty or healthy. If you feel an overwhelming desire to be thin, then get some help. Call your doctor. If not, then dump the junk food, avoid sugar and exercise. Good luck!