Caitlin, this site will help...
http://www.al-anonuk.org.uk/
It's not anyone's fault. These things happen, but it's down to the person to decide how to deal with it. Al-Anon is for families/friends of people who drink. They're a really good source of info and support.
Edit to add:
http://www.al-anonuk.org.uk/alateen is the part which will possibly be more relevant to you since you're young.