Sexual harassment or No?

So recently I've been having some issues with one of my coworkers. We were on pretty good terms, she seemed decent enough and I invited her to my house for girls night with a few of my other friends, some of them coworkers as well. Our job switched all of the employees desks and I ended up next to a man who she apparently had been sexually involved with and she did a complete 180. She contacted me on social media and asked that I not discuss anything about her with the man then started telling me to screw him already, telling me to "shut your cocksucker" and calling me a cunt. Recently she's progressed into telling some other coworkers I am "fucking him and other men". I'm not sure if this would even be considered sexual harassment in the workplace or what it is. Thabks in advance, any advice would be greatly appreciated!