Is it safe for a teenager to do Insanity?

my little sister wants to do Insanity with me, but it's very intense. Is it safe for her? What're some precautions she should take, if any?
I read somewhere that she might get joint pains. Is this true?
Sorry, so many questions, hahaha. I'm just concerned about her doing it!

why wouldn't it be safe? is there some downside to teaching children strength, form, improved muscle ability and athletic performance that I'm unaware of?

If anything, it should be easier and better for her. She should be healthier and fitter...

As long as she practices good form and doesn't cause herself any injuries by landing funny or twisting her ankle or anything i see no reason for her not to be able to do it.

As a martial arts teacher we advise against people who still have developing joints (or where they still have a while before being full grown) to avoid some things that could damage the joints. I don't see anything of that nature in the insanity workouts. The things that we avoid are like finger tip push ups (when instead of haveing your hands flat on the floor you support your weight only on your finger tips) and other things that will put a lot of strain on the joints. I hope that this helps.

I should add that by about 13 we give them the green light to try these things if they wish so if she's older than that I would say there shouldn't be any thing to worry about.