Dh was a heavy drinker when we met and was until kayleigh was 1. He stopped on his own when he realized how immature and expensive it was of/for him.
My sister was also addicted to speed and did acid in high school. my mom was useless for her at the time, and so I was the only source of support for her, poor girl.:(
though i supported her and listened to her talk, she did have to hit her rock bottom, and she REALLY pulled herself together andis now a wonderful human being and then some.
remember, janey-it's not YOUR problem, or YOUR fault or YOUR choice, it's your mom's. It's so painful to see them go through this, I know. (((hugs))) Have you checked out al-Anon? this is support for families of addicts, and can likely offer some great advice for YOUR position.
best of luck, and even if she never snaps out of it, keep loving her, and most importantly, love YOU.
Keep on keepin' on...