Explain changes in speed of rotation for correct body placement.
Talk about entry into front tuck and how you if you want to land on your feet you need to rotate fast enough.
Show video of her doing this landong on a crash mat. Get her to land on feet, over rotate to fall forwards and under rotate too and on her bottom.
If using an iPad my favorite is Instant Replay as I find their scroll forwards and backwards at whatever speed you move your finger really nice to use. Very tactile.
Then get a volunteer to stand up the front.
Ask them to stand with arms outstretched and turn on the spot. I'd kind of be ready to spot them when they start staggering, then ask them to pull their arms into their sides and watch the change in rotation speed. Get them to do this few times with different speeds of pulling the arms in. By this time they'll be dizzy which will amuse the class.
If possible, and if there is enough clear space that you feel it is safe, convince the teacher to be the demonstration subject.
Edit: depending on age do the calculations for angular velocity etc. if not, it's still a nice demonstration.