It depends on which path the MP said how a false friend can behave
MP's words
1) he simply tells Anna and David the truth of what he’s learned; 2) he doesn’t say anything... instead he tries to conquer Anna while she and her marriage is at a low point; 3) he dangles the info in front of Anna, but he won’t disclose the truth until she gives him something in return.
Knowing Chris, it doesn’t seem likely he’ll go with option 1. Rather, it appears option 2 is his preference. However, if Anna’s more reluctant towards him, he may go with option 3.