So, my step-son's mother is starting rumors that I am stalking her because I got hired in to a place where she used to work. I never knew her before I met my husband, but now she calls and harasses him and is starting to send "people" to my place of employment to harass my boss too. I think that she may be a border line stalker and I just need to know what constitutes harassment and what can I do if it continues..

... I just need to know what constitutes harassment and what can I do if it continues....?

To answer that question, one would need to look at the criminal statutes in your state. Which state is it?