I believe 2 months is enough to develope a real bond with or fall in love with some one. today marks one year with my girl friend, and it was at about 2 months that i knew this was for real. One year and we couldnt be better.
Now on with the drug situation. Dont leave her, you might be all she has as far as her hopes of getting out of this. People do clean up. and clean up for good. If you leave her because of this she might look at that as her last inspiration out the window and fall deeper into this. I can only imagine how much this hurts you. You obviously care alot about "B" and i think its the best for the both of you if you stick with her through this. Keep it in your prayers and i'll keep it in mine.
If she chooses the crack over you you may loose the love relationship, but dont just give up. Stick with her as a friend, Like the theropist said, you could be her godsend and she needs you.
I hope it works out for both of you. Keep us updated