Grounds for slander or something else?

I am 46. My mother and I had a "falling out" almost 3 years ago & have not verbally spoken since. It was regarding why she treated her loved ones so badly. No-one has ever stood up to her b4. She has since sent me many emails calling me horrible names, calls me crazy, & says I must be on drugs. She ends the email w/ "have a great life" & that she's never going to talk to me again. Aprox. 3 mo. later, I'll get another email w/ the same name calling & saying it's the last time she's going to contact me. (This has happened numerous times.) I am Not on drugs, Not crazy, & Never lied to her. If I ever responded to her it was in a very calm manor even asking her to leave me alone. I just found out she has sent a letter my 24 yr old son telling him I am on drugs/crazy. She told him EVERYONE that she knows agrees. (Because of what shes telling them.) I have kept my mouth shut all this time! This has got to STOP! Do I have grounds for a slander suit? If so, is this what it will take?