I can see why he did it. He is now famous. But tell me why she did it? Doesn’t look like she got much out of it Except being posted all over the net for the rest of her ife.
The plane? Yes. Clowning around like that sitting right next to the pilot could have either distracted the pilot or they could have bumped into the controls.
The parachute? Not at all. It’s a very common technique for students and instructors to skydive in tandem like that harnessed together. So as long as one, or both, are experienced skydivers, it was no more dangerous than any other “stunt” such as a group diving in a formation, which is also fairly common.