My 1/2 cent-

I agree w/ the suggestion of a 20 ga, but make it a break open gun (O/U or SxS), as they're:
1. better for teaching gun safety
2. safer guns for beginners (you can tell from across a field if the gun is open)
3. much less likely to pinch her little fingers

Then, start her w/ these shells:
Fiocchi Premium Target Loads: Low Recoil Trainers 20 LITE
http://www.fiocchiusa.com/cat_target.html


Always looking for small bore Francotte SxS shotguns.