My friend is cutting herself?

[devon d]

My friend has always been a happy person. She recently had a boyfriend who wanted to dump her. So, he called her home phone and left a message. She frequently spends more time at her grandparents house then her mom's, so she never heard the message. Then, over AIM, someone was like "Sorry about you and ________ (boyfriend's name)" and she was like "What?" and found out that he had broken up with her and was telling everyone she was a lying skank and a slut. I guess she really liked him because she went into emotional breakdown. I had no idea about any of this until today. We were changing in the bathroom and she asked me if she told me something if I promised not to tell and then she told me she was cutting herself and showed me the cuts! SOME OF THESE ARE DEEP! IT LOOKS LIKE SHE MIGHT KNICK HERSELF (which in my school means hit a blood vessel leading to unstoppable bleeding). I'm really worried about her, I told the guidance lady but she isn't doing anything.
She only started on Monday, but her whole arm is almost filled up. Every night she goes deeper.
I mean both arms are almost filled up. Kinda looks like someone with razor sharp nails has been scratching her arms.