What would you do if you found out...?

your best friend of over 10 years talked smack about you and then accused you of doing that to them? I recently found out that someone that I thought was my best friend of over 10 years has been talking smack about me behind my back to other people. I mean she then turned around and accused me of doing it to her when I haven't. What makes the matter worse is the fact that she wasn't just doing it with other people on the phone or whatever but she was posting stuff on the website Xanga talking smack about me. What she said were mostly lies and what is true was started by her. She's made me look like a complete jerk to complete strangers and made herself look like a complete angel, when she is nothing but a scandalous witch. What she had posted on Xanga was posted long before she accused me of talking smack about her. I have already ended the friendship, but I was wondering if maybe there is a good chance that I have a case against her for slander. What do you think?