Jason - I can relate, actually. My my sister, a year younger than me, got into such things when she was about 17. Moved out of the house, in with the people she was using with, and broke my mother's heart. Over the year or so it got worse...she went for harder and harder stuff, randomly took off fo New York, then Miami for six months with some boy we'd never met...you name it, she did it. The only thing she never did (thank god) was get pregnant.
My mother felt like her child had died, and it was all her fault. Since my father was buried in his work, it fell to me to support her and try to convince her that my sister's behavior was NOT to be blamed on my mom. It was 18 months of pure hell, and part of the reason I moved back to my home state to finish college. I was mad as hell at my sister for putting us all through it, and for wounding my mother so badly.
But there is a light at the end of the tunnel...my sister has pulled herself out, quit the heavy stuff, cut back on the booze, and has held a job for over a year now. In fact, she now manages the coffee house where she started work. The relationship with my mother is on the mend, and life is returning to normal.
So take heart...and tell your mom these things CAN get better.
You guys are in my thoughts...