Long story short, dated this girl for almost two years, she cheated on me, I broke up with her about a month ago. Now she and her mother are always posting on Facebook/telling people that I cheated on her and I was a liar, etc. Of course everyone believes her, making me look like the bad guy and hurting my reputation. Is this considered slander and, of so, what are my options? This is in Oregon. I'm 22, she is 21.

Edit: I also have screenshots of our conversation with her admitting that she cheated on me.