That's not something you tell someone who cuts... I would know... I use to cut... Was going to attempt suicide but then my gf came into my life... She is really the only reason I'm still alive. But guess what she cuts too... The best thing you can do is try to get her to talk about her feelings or ask her what's wrong. Let her know know that you care about her without actually voicing your concern by listening to her (not saying you haven't) but most girls just want a guy who cares and has a tender heart.