i would not ask to show the cuts... cause 1 it might offend her, like that's all youre interested in, or 2 if she is just doing it for attention then youll be giving her what she wants "oh they think its cool"
so i would suggest you guys just confront her calmly, don't make her go into defensive mode, and just say that as her friends you all really really care about her, and that's why you want to talk to her about helping her stop injuring herself... 'we might not understand what you're going through, but we want to help because what you're doing isn't good for you'