That’s what I initially thought but I did some reading and it’s not really the case.

Firstly, the age of consent in france is 15, and the attitudes of the French people are much more relaxed in this area, and I can respect that.

However, it’s likely there was some kind of relationship when he was 15 and she was 39. There’s no evidence that it was sexual but I kinda assume that it was. His parents sent him to a school in Paris to break them up. I can’t be bothered linking the source but it’s mentioned on the wikipedia page and you can click through to read the references.

On balance, it seems no laws were broken and it seems unlikely that either party was harmed. However, the early years of their relationship were certainly dubious ethically.