I would guess that there is no law against doing what the woman was doing. When would lawmakers ever think that someone would do something like that?
Doesn’t matter. Flight attendant instructions are rarely codified law. Anything you do in a plane that starts a disturbance can be addressed by them. If you refuse to obey, it’s illegal to disobey instructions of a flight crew.
Bestiality is probably against the law, but I’m not sure if this qualifies. It is getting close, though.