Unless you have your heart set on the .257 (or a .25 cal), I would recommend something different...I would check out Remington's line of Managed Recoil loads for larger caliber rifles...I have experimented with the MR loads in .270 Winchester (a .277 115 gr core-lokt at lower speeds) the recoil is slightly less than a normal .243 with a larger bullet diameter. Performance is limited to about 200 yards or so...

However...

As she grows older, becomes more familiar with the rifle, and perhaps a bit larger, she could switch to full power rounds for better performance at longer ranges or even the Hornady Light Magnum rounds if larger than deer sized game is called for...

If elk, bear or moose were also possibles at some future date, I would recommend starting with the MR loads in .308 or better .30-06...

One gun...with a wide range of capabilities...