What should I do? Need advice to deal with my best friend.?

My childhood friend cheated on her husby whom i know well. I thought she was moving on and trying to make her marriage work but she then told me shes still pining for the guy she cheated with although it ended badly. Shes living in lala land and she hasnt told her husband the truth. Not to mention shes been flirting and playing with fire kissing other ppl. I dont want to hear this stuff its dissapointing and heartbreaking. Any advice on how to handle this?? Thanks.