Cath, when I was 16 my mother had to go into rehab and I went to live interstate. Mum was sick and she needed help. It was absolutely the best thing she could have done for me. I had stability in my home environment and she had the space, time and support to recover. She wrote to me every week; little cards, poems and thoughts. Mum is back on her feet and kicking butt as a Masters student, and we now have a loving and close relationship.
Your daughter will thank you one day.
As for depression, it's a tough one but can be managed. I have major depression and alcohol just makes it worse. I used to kid myself that it was taking away my pain, but in reality it just adds to it.