i feel for you. i have 2 daughters, both are just normal teenagers (actually i take that back...they are respectful, intelligent, teenagers not interested in anything but school and their friends right now...which for aussie teenagers is rare...most are boy crazy)...but i hope i never find myself in your shoes. you seem to be doing the right thing for yourself and your daughter by the zero tolerance stance. it would be a very tough situation to be in, but for your own sanity, im guessing its the only one that will save you, and i hope, your daughter too.
wishing you the best and hope for a good ending where she can make good choices for herself.