To be or not to be

I have a friend who is married to a man that cheated on her before. So she tried to spice up their love life by introducing a third to their group. It was fun for awhile but then she felt like she was being pressured to keep it up. So she ended the whole thing. After several years it came out that their so called mutual friends liked her husband and even admitted to having a crush on him and being sexually attracted to him. They have had their ups and downs. But one of the girls from the group tried to take things too far and tried to continue it after being told it was a no go by wife and husband. So after some time she messaged wife to apologize but also befriended husband again now she has taken to messaging husband again and sending him stuff of a sexual nature which he sends back. What are your opinions?