When they finished reading, I explained that I had discovered the text messages and pictures that she was sending our son, and that according to the laws, they constituted distribution and possession of child pornography.
The concept of sex differences has deservedly received a lot of scientific debate, and it's important to tease apart socially constructed ideas of gender versus actual gender differences.
I had to find a way to scare them enough to keep them apart, but keep the upper hand so that they would maintain their distance.
More: It turned out this young lady, who was a few months shy of turning 18, was the only one sending pictures.