I found out my girlfriend cuts herself. She has been doing it for quite sometime now she tells me. And she made me promise not to tell anyone. She is also starting to take large a mounts of typical Tylonal or Motrin painkillers. And she hardly eats. The only person I told was my mom. Should I tell her parents? Or would that make it worse?

I would find it hard to believe your mom did not already tell her parents, why not, have her do it. But if not, yes they need to know, she needs to get professional help.

Her parents need to know. She is harming herself. She may get mad at you, but you need to report it. If you don't want to tell her parents, maybe you can tell a teacher or counselor. You could also ask your Mom for some help. Cutting is a sign that someone needs professional help. You may be saving your friend's life. Let me know what you decide to do.