No matter how negative a neighbor is; you will only come out ahead by keeping your cool.

I strongly suggest that you determine your rights by law. I don't suggest addressing your neighbor at a legal level, however it is imperative that you know your rights and so that you know what actions she has taken which qualify as illegal. It is good you are keeping notes on incidents and associated dates. Make sure to preserve the social networking evidence on both Marijuana (which notable may be legal for her to have) and most importantly abuse of other drugs or alcohol. I am sure this will assist you if and when your neighbor forces a legal situation upon you.

I would recommend speaking with the neighbor that is now leaving you alone; perhaps they can give you insight into the deeper reason that the second neighbor is still acting out against you.

Being the mature party is hard, but if you can figure out their real problem, then maybe you can address it.

Be safe; don't break any laws!