ORIGINAL: 20GADBL
but if it kicks to hard she won't want to shoot it.
Before you go spend your money on a rifle and find out it has to much recoil I would say, see if you can borrow one from a friend and let her try it. It would be a shame to spend all that money on something she wouldn’t want to hunt with unless you had that included in your plans and just have to keep it for yourself...