Firstly i am very pleased that you and your girl are finally got that meet and are getting on very well! Sounds like you have a good one there! But as we all know where there is good there is bad and in your case she is on coke. My sergestian for this would be try and talk to her and perswade her to get help i am sure that you will be more than supportive for her i like you dont think that you can dump her as you have been through alot and the coke thing is clearley messing her mind up i am very sure that you will be able to sort her out and if you succede than you will have a near perfect partner!
I apologise in advanced for my atrocious spelling. The advice or View I give probably wont be much good but it may help some one make a good suggestion!
Cheers Steve