Not to interrupt this productive exchange, but back to the question at hand:
I am in the .223 camp if a new rifle is an option. I set my wife up with a .243 T3 compact only to find that she likes shooting my .223 much more. It's the muzzle blast as much as the recoil that causes flinching and makes the experience unenjoyable, and there's really no way to reduce that much in a .270. Muzzle brakes are really counter productive for that.
If a new rifle is not an option and you reload, you could try the light TTSX bullets. I wouldn't even drive them too fast. Shoot for 2800 or so. They're meant to expand at 6.8spc velocity, so no concern there. They'd pretty much match .243 recoil energy.
If you don't reload and are sold on the .270, use 110gr ammo, add a limbsaver recoil pad to your tikka, and invest I GOOD ear protection. Also, make sure she doesn't shoot too much off the bench. Bench shooting amplifies recoil.
