My once good friend

she use to be the best friend ever, I went to her for everything. We got into some trouble together. The problem is I learned my lesson, she didnt. She has always been jealous of me & my whole life. I cant stand it. Now she is sleeping with all my ex boyfriends. I told her specially not to sleep with one guy , & she tried. She is only 16 & she drinks alchol everyday & she is really sluty when she does. She tried to commit suicide. She is already on probaton & when she was on she got caught stealing. Her dad is even sending her to boot camp. At first I just quite being her friend, but now I cnat help but to just feel bad.

I was ready to help her till she started sleeping with all my ex boyfriends. She says ohh I was just drunk , but when I broke up with my last ex boyfriend , she tried to do stuff with him when I told her THAT IS ONE GUY I DO NOT WANT you MESSING WITH. I STILL HAVE FEELING FOR HIM. & she agreed , she was even the one I went crying to when he hurt me. Then as soon as I Leave for the summer she is trying to hook up with him. Luckily he didnt do naything. But I still heard it from friends & stuff sjhe tried. Now me and him are going back out. But she is just too out of hand.

How do I deal with somene like her?