My sister married my ex-husband of 12 1/2 years. Is it ok that I'm not talking to her anymore?

I left my husband after 12 1/2 yrs. His constant affairs and our constant fighting were enough. So I found out that my older sister who was also married began having an affair with my husband 2 weeks after I left him. Yes, I left him - but shouldn't your sister just NOT do that to you??? And so they are married now and they don't want my kids to call her "aunt" anymore. I just don't want her to have anything to do with my life now. I'm remarried and happy but still don't want her anywhere around. Am I wrong?