Should i just ditch my so called "friend"?

...i told her about my self-harming problem...at first, she didn't believe me, so i just rolled up my sleeve and showed her... she started laughing... she said i looked "so " and that she hopes i keep making new scars to keep that "status".... i was really shocked... she had really been a good friend and everything... i don't know if what she did was just out of shock, or what...next day, she shows up to school wearing "emo" clothes, synced screamo music on her ipod, with her new skull patterned headphones.... (she never dressed like this before... she always had a very casual style).... i found it kind of insulting... the reason i told her, was so that maybe she could help me... i thought it would be healthy for me to tell someone... but apparently not.... and now, because my "friend" couldn't keep her mouth shut, the news of my cutting issue has now spread around to people i know from my cles....soon, the whole high school will probably know... but i'm not so worried about that spreading around, more so just saddened by my "friend's" reaction.... she seems to be acting very y, and egoistic now, like she's so ", and cool" now... it really bothers me...should i try and forgive her, or just tell her straight out that i don't want anything to do with her anymore...???? i'm very shy, so i barely any friends...which is why i usually forgive people easily, because i don't want to be left completely alone... but with this, i'm skeptical...i don't know what i should do ????