i think the 270 or 7mm/08 would be ideal.If she did pursue elk than shot placement would be critical and bullet choice would need to researched.Both of these calibers have killed plenty of elk.try and find a good stout rifle of 7pnds or more,avoid a lightweight for her.this will help manage the recoil for her.some suggestions rem 700,savage american classic,thompson icon,weatherby vanguard,.
I would go with a 308. You can get great ammo selection, and can find it almost anywhere. You can always get a recoil pad if it too much. Or go with a 270 with a premium bullets and the 270 will drop them also. Good luck.