One thing I did not mention directly .... one of the often overlooked qualities of a long gun associated with recoil "comfort" is the length of pull, often abbreviated LOP. You mentioned "short". It might be wise to have the stock cut to fit her LOP, including the length of a good recoil pad. Another strategy could be to ease her into shooting ... say a 22 rim fire at the range plinking cans. Practicing with a 22 LR certainly will not hurt her shoulder and might get her used to the "pop" .... sometimes the "blast' is as much of a scarey thing for a newbie as is the recoil.
I know others will disagree with me, but I do not consider the 223 Rem. a good deer round. Will it kill one? Sure. So will a 222 Rem. or 22 Swift or 22 Long Rifle for that matter. I just do not care for 22 cal. on medium sized game when there are excellent, relatively low recoil rounds out there such as the 243 Win. that are excellent deer rounds.