My husband had an online "affair" on Facebook-his family has remained friends with the other woman.

My husband had an "affair" with an old classmate he reconnected with on Facebook. He and I are working things out and the relationship is over between the 2 of them. The other woman is still friends with his brother, sister in law and other mutual friends-and loves to comment frequently and is in my face daily. Am I out of line in thinking it's inappropriate for my in laws to still be friends with a woman who was urging my husband to leave me? They aren't just online friends, they spend time offline together as well.