7mm-08.......Is a good choice...
And probably be the smallest cal I'd recomend would be the 6.5-284...
My bro has shot elk seberal elk with the 7mm-08 cal..(within 200yrds)lots of deer out as far as
400yrds..Moose and Black Bear as well....
I watched him dump one moose(700lbs)at 325 yrds away...
But if she could handle a .270 or greater it would be a wise decision......Addition of a recoil pad and or muzzle break will certainly help her being recoil sensitive when shooting a bigger cal..
But the most important thing is getting a gun in a cal she is able to shoot confidently...(As you already know)........