C9 - Sorry to hear this, my EW did the same thing although I had no clue. While it hurts I wish I would have known back then so it is good that you have the intel. I would suggest that you don't snoop and try to find the pictures yourself. I would also let your friend know to keep these things to himself moving forward.
Truthfully you don't do anything other than to decide whether or not you want to move forward with D yourself. Since you are separated there is not much you can enforce unless her dating is a deal breaker for you.
