She is reeling - just as you are. She deserves as much sympathy, care and consideration as you do. She ISN'T doing this TO YOU. She is doing it because she can't control herself and is in terrible pain. HE is the one who used it to reach out to you. HE is the one who made it your problem. For that matter, she may well not even know that he reached out to you and would be angry and humiliated if she knew.
If she wanted to hurt you she'd be on your Facebook saying awful things, calling you, exposing you at your work and in every facet of your life. But she's not - instead she hurting HERSELF as many of us do after our WS breaks our heart. Have compassion for her. Focus all your anger on HIM. He's the one who brought you into this mess. Before - and now. I can guarantee you that I compared myself to my husband's AP (she's not as attractive but she is younger) - but my husband talked with ME to remind me that it didn't matter. That I was who he wanted and desired. That it had been his need for attention that had made her attractive - not some lack in me. He did NOT call the AP and tell her to block me. He had gone NC and was keeping it that way for EVERYONE's sake. Your ex-AP contacted you because he wants you thinking about him... and he feeds on the drama of it all. This is not HER fault.
BS - Female
Married 27 years, one adult child DD May 2016 “When we are no longer able to change a situation, we are challenged to change ourselves.” - V Frankl