I was a self-injurer for 9 years, and I've been away from the razor for about 3. I can tell you that those look like healing wounds, and they look just like the cuts I would leave on myself. On the other hand, if she was really a self-injurer, I'd be pretty surprised to see her wearing anything other than long sleeves to conceal them. I say they're cuts, but you never know.
Idiot.