I would go for the additional RAM and storage capacity based on what you say your GF does. She is less likely to have to worry about space left and a program or two having swapping issues due to lack of memory. If she needs Windows, she can allocate a proper amount of space to both OSes as she sees fit. You can't do much with 64GB which comes to 60GB usable.
I don't own nor do I see myself owning a Thunderbolt storage device anytime soon, so I don't see the point in that feature. For me the miniDP would be fine.
The Core 2 is still a powerful processor. It's still capable. For a lot people, I don't think they could really tell the different.
The backlit keyboard on the newer model is just something else that can break. No serious writer going pecking for keys, so why would she need the backlit keyboard? Personally I have that feature disabled on all my computers with it. I sort of wish there was an option we could order that read "backlit delete" or something like (much like a "model delete" when you purchase an automobile and they debadge your vehicle).
Good luck!