My ex-boss keeps running her
Mouth about me although I'm not longer employed. She continues to say things such as, I only quit because I couldn't pass a drug test and that I'm trying to convince other people to leave, etc. Should I pursue this into a lawsuit because I'm afraid it is not only hurting my reputation but could affect any future jobs I may get. There is also another girl she is doing this too. Also, if I did push this farther, what kind of proof would I have to have to make my case?

You may have a case, it would be up to your boss to prove her statements are true. You just need to prove she made them and that you were damaged by them. Consult an attorney.

Perhaps, if this is a large company have you filed a complaint with HR or the owners of the company?

Is there any truth at all to what is being said, remember it is OK for her to say things that are true.

None of it is true. Not once have I contacted any of her former employees trying to get them to leave, nor do I do drugs. The company does nothing, I have people that has messages from her saying it, and also have people she has said it to. Would that be good enough proof?

Saved messages and testimony should be enough proof she said those things, but harder will be showing you were damaged by them.

But you can't process a case like this on your own. You need an attorney. When you consult with an attorney they can better advise what is necessary to prosecute this case.