Children of Addicted Parents and People

hi, my name is Jessie, and my mum is a alcoholic and is also addicted to various types of drugs.
for all my life (im 17, nearly 18) she has been this way, but when i was younger i diddent understand, and i think it has progressivly got worse. i lived with all her shit and her continous fighting (both verbal and physical) with her boyfriend until i was 13. and i told her i cant deal with it and moved out with my dad. dad and i have always been really close.i still seen mum about 1 a fortnight, but i never stayed at her house. dad was remarried,(to Sandy) and she hated me for some reason, all i ever did was try to get her to like me. dad had a divorce because she told him to choose, her or me. when i was 15 i met my boyfriend Zack and moved in with him. i came closer to mym...but only seen her during the morning when she was still sober. one week we would be really close and the next day she would get smashed and ring me abusing me saying how much of a dissapointment i was and she wishes she diddent ever have me. (even though she was on IVF for 4 years trying to conceive) and then she would apoigise and i would forgive her until next time.
she finally moved out form her boyfriends house abut 4 months ago and in with my grandma, we still had the same on again, off again relationship. but 4 days ago she wet out to her friends house and got blind, and came home the next morning abusing grandma and me. i found her stash of drugs and alcohol and got rid of it all. sent her a message saying i never want to speak to you again and im sick of all her empty promises, and abuse...it went for about 11 pages i think.
how do i stay strong and not talk to her and not forgive her when all i want is to have her back?? the real her, the sober her.

i cant stop cying, im depressed....i hate this but what else can i do, she is never going to change. she is too far gone