Turkeys can be killed with a 20 Ga. with standard 2.75" #5 or #6 loads.

Today's recoil pads do work well.

Get her plenty of practice to be sure she's aiming correctly on a turkey target. That will also verify her maximum range to get 10-12 pellets in the head/neck.

I'm assuming you will be sitting right next to your daughter. If so, you can make sure the bird is within the effective range of the gun and load, then give the go-ahead to shoot. You can be ready to back her up if the bird shows signs of getting on its feet.