4
What should I do
As little as possible.
Since they are best friends, I assume there isn't a large age gap. So I think that whatever they were doing happened because both agreed to it, and was legal where you live. IMO, that's the most important thing to establish. If you have any doubt about this, you should intervene.
TL;DR: The important stuff
The ...
Only top voted, non community-wiki answers of a minimum length are eligible
