re: What to cook for people who have very little exposure to good food

It's not a matter of "growing up" for a lot of people. As you say, some simply are not exposed. It's never too late to try things and it's perfectly okay not to like everything.

You know her better than we do. I wouldn't start with lamb unless you know she wouldn't have a problem trying it. Might work that in later on at another meal after you've cooked for her once or twice and get more of a feel for how adventurous she is and maybe after she's had a chance to be more adventurous. I like the beef short ribs idea. Maybe some more adventurous sides like a roasted beet salad Lilette style, a quinoa dish or something along those lines. No need to shock her on every dish. It's no fun to cook a meal for someone and have them not enjoy at least something you made and it's no fun for the guest to leave hungry if there's nothing she might like. A balance would be good for the first time cooking for her and then you can go from there. Main thing is to make it a fun experience either way and it will probably go very well.