Perhaps it bothers you that she is going to the ER for these self-harm injuries, and you feel the injuries don't merit an ER visit? It sounds like your friend is in quite a bit of emotional pain, and perhaps self-harming and going to the ER gives her the attention and care that she so desperately craves.

Forget the physical wounds for a moment, and think about what state of mind you would need to be in to harm yourself and then run to the ER multiple times. Your friend is hurting, a lot. Maybe you could try empathizing with that? Also it would be helpful to not give her any more self injury "tips" and rather try to show her that it isn't the only coping mechanism available to her.

If you continue to want to see her hurt herself more, for her sake, please break off the friendship.