Bobby,
Perhaps you should not be so dogmatic about your girlfriend's rifle selection.

Let me tell you a story. My wife hunted for years and killed many whitetails with her Marlin .30-30. She has also used my .270 and .30-06 and killed deer with both. Last year she decided that she wanted a new rifle. When I asked what caliber, she said ".270." She had made up her mind, and I did not interfere. She found a very nice .270 Rem 700 BDL. She loves this gun, and shoots it like a house afire. This accurate shooting is very important, since accuracy begets confidence. which begets accuracy, which... you get the point.

I have hunted over much of the US during the past 49 years, and have killed whitetails, mule deer, elk and antelope with both calibers. I give a slight nod to the .30-06, but there is nothing (except possibly a grizzly) that walks in the lower 48 that cannot be dispatched quite handily with a .270.