The above posters pretty much covered it. Any cartridge with the same (commonly called "standard" or "308 sized") head diameter will work, and preferably staying with a long action round.
Two other considerations for your girlfriend.... by your handle it looks like you may be a student, and therefore watching the funds for now, but if possible consider a "smaller" round. Something like the 243, 260, 7mm-08, etc. By the time you figure the cost of a rebarrel, you can probably find a used Savage for about the same cash output, and have an extra rifle. Figuring though that may not be an option, yet, think about either handloading some lighter 270 rounds (a 110 grain bullet at a slightly slower velocity is a pussycat), or look into the Managed Recoil or Reduced Recoil factory offerings. They basically do the same thing (lighter slower bullet). Start her off right with something she's going to enjoy and she's much more likely to keep shooting with you.
Have fun shooting with her, and good for you on trying to get another female involved in shooting (even if there are alterior motives....