Do I have to?

I had an online affair with a man in Europe. It ended last fall when he was caught jerking off in front of the computer by his wife. She was so mad at him and wanted to get back at me. I don't blame her. I was happy to stop the affair and go our separate ways.

She was so angry and blamed the affair on me so she started to cyber-stalk me and would find me on the public sites to harass me. I am a professional and could not have my private life strewn all over the internet so to make a long story short. I became friends with her and now I have to no choice but to be nice to her. I would rather just ignore her on my social network, but I can't. She leaves me things in my inbox and writes messages to me on my IM. Do I have to keep this up? Her husband and I have no contact. He did tell me that she is being genuine and I totally believe him, but why do I want to have nothing to do with her? I wish she would just leave me alone. I can't be on chat anymore because she waits for me to show up. There are other people that I would love to chat with, but I don't want to converse with her so it is better to be offline all the time. I know I am being whiny, but do I have to be friends with her? And is there a nice way to remove her from my social network?