Totally know how you feel. 2 weeks after my H ended his A with the last OW she was posting pics of her and new bf and talking about how in love she was and how perfect they were for each other.
They lasted 3 months. She's had at least 2 others since him and is currently single and has several active online dating accounts (that seem to be generating very little interest). She is jobless and single. She is headed back to school in the fall to get the degree I've had for almost a decade. Her posts still seem happy, but I know better. Her facade will come crashing down someday and everyone will know what you have known for years. She is a miserable, broken human.