15 yr old DD -- truancy and online friends

[shoppingtrolley]

My DD has deteriorated since turning 13 and is now falling out with everyone, terrible mood swings, obnoxious at home, hormonal and addicted to the internet. She has started refusing to go to school and I fail to make her go, and now she is missing out on substantial quantities of work. She has a 17 year old boyfriend who she met online and seems to have no ambitions, no aims or dreams. She looks terrible and sometimes cuts her arms. Is this normal or teenage stuff or are we having it particularly bad? I don't know as I don't have many friends with kids the same age.