I purchased an 20ga Pardner Pump all black for my daugther. It shot really good patterns with the jellyheads with 3" Heavy Shot magnum blend , good enough I didn't try anything else!
But the guns my carry the same name but to say the Jellyhead would work the best for you would be wrong. Each gun and ammo combo can be different.
I know it sounds kind of strange to buy a cheap gun and spend so much on the ammo and choke tube but to be honest I had no idea if she would turkey hunt any after her first time last year but we are going again this year and if she didn't I would have a 20ga to play around with.
You don't have to spend big money on a gun I have an 870 3" I bought more than 10 years ago and it patterned better than my brothers NWTF Browning Gold edition. We never could get than gun to pattern no where near as good as mine no matter what we tried!!!!
I don't think you should skimp on the ammo or choke tube find what works. Heavy Shot may be exspensive around $5-6 a shot but I have gotten my best patterns out of my 870, my sons Mossberg 500 and my daughters 20ga with that ammo. I have a Jellyhead on my 870 and the Pardener but Mossberg is a different and cheaper choke but it worked great!!!
No I have not let her shoot those 3" shells I am doing her like I done my middle son we go out and shoot the lightest target loads I can find and I told both of them the samething that it will be no difference in kick. My oldest son at 10 years old I think he would have shot a canon if he could have found one and been able to shoulder it, he was never afraid of recoil from a gun.
First year turkey hunting for my middle son he harvested a 3 bearded jake, and said he didn't feel the kick on those 12ga 3" magnum loads.