Why i sad. (08022012)

My girlfriend today take a ruler and cut herself. and she dun know I am looking at her. and after school I go home and sms her and ask her 'why you wan to cut yourself' and her reply 'fun' and i tell her 'this not fun at all and this is hurting yourself' and now her sms me and tell me ' I will not cut again if I cut again you slap me' and i say 'no. i will angry and say you' and her 'call me to stop her also'. really sad.