She won't notice the recoil difference between any of the calibers you've listed. Both my daughters shoot the 7mm-08. My youngest doesn't weight 90 lbs soaking wet and is real small framed. There's only .5 mm difference between the .260 and the 7mm-08. Both are built on the .308 case. The .260 is practicly identical to the 6.5 swede. Given the choice between the two and I'd opt for the .260(ammo availability and prive). The 7x57 is a great cartridge but will have slightly more recoil than the other choice including the 7mm-08(again not enough that you would notice).

What I'd do is take her out to try rifles for fit. Once she finds one that really feels good see what caliber it's offered in. She'd be well served by all of the calibers you've considered thus far.

You see rifle fit and weight have more to do with felt recoil than the caliber does. So find a gun that fits her and that she likes and go from there. One more thing. I'd stay away from the Ported recoil reducer muzzle brakes. They are very hard on the ears and cause more flinching problems due to noise than most shooters would develop from the recoil itself.

Good Luck!