When I was eighteen I lost my father, I also used drugs/alcohol to cope, in fact the night he passed I went on a binge blowing all of my money for bills and extra money I could have been using to help out with his funeral costs.
Thankfully I had a loving group of people that I worked with who noticed the changes in me and helped me help myself. Although I didn't quit drinking after this it helped me understand the stages of grief and I cut down on my drinking because I was not doing it solely to cope with my loss. Believe me I was pissed at first they pulled me into this room and gave me a pamphlet if I remember correctly I think I may have even thrown it back at them insisting there was nothing wrong with me, knowing deep down I was in a lot of pain.
I would suggest going to places you might have gone together and talk to her or write her (this is something I use to do often whenever I felt the need to talk to my dad, it helped me very much). It will get better I promise.